Documents de travail
There is no consensus among economists about the reasons why firms resort to profit sharing compensation, especially in larger firms. This paper presents evidence for France showing that firms with unions are more likely to resort to profit sharing than those without and, moreover, that strike incidence decreases with its usage. Inspired by these stylized facts, I develop a model to study the effects of profit sharing on union behavior that introduces two novel mechanisms. First, by making employee compensation depend on output, profit sharing makes unions internalize the cost of their strikes so that they are less inclined to organize collective actions. This in turn damages the credibility of their strike threats. Second, over time unions lose reputation, which further reduces their bargaining power. Lastly, I test the model using exogenous dates of elections of union representatives that give incentives for unions to organize collective actions in a competition for voters. I show that employers anticipate the effect of elections by increasing the usage of profit sharing. Its payment leads to a reduction in strike length the same year, and to a drop in wage growth by about 13 percent the year after. The effect is concentrated on lower occupations for whom wage growth is almost halved and driven by a reduction in the bargaining power of unions.
In this paper, I introduce a workable dynamic utility model on the interplay between economic actions and social roles. I model both how economic actions are embedded in social roles, and how social roles reciprocally feed back into preferences and affect economic outcomes. I also consider a set of policy interventions aimed at breaking social roles when they deteriorate economic outcomes.
This survey paper reviews the recent Bayesian literature on poverty measurement. After introducing Bayesian statistics, we show how Bayesian model criticism could help to revise the international poverty line. Using mixtures of lognormals to model income, we derive the posterior distribution for the FGT, Watts and Sen poverty indices, then for TIP curves (with an illustration on child poverty in Germany) and finally for Growth Incidence Curves. The relation of restricted stochastic dominance with TIP and GIC dominance is detailed with an example on UK data. Using panel data, we show how to decompose poverty into total, chronic and transient poverty, comparing child and adult poverty in East Germany when redistribution is introduced. When a panel is not available, a Gibbs sampler is used to build a pseudo panel. We illustrate poverty dynamics by examining the consequences of the Wall on poverty entry and poverty persistence in occupied West Bank.
Given the importance of continuous follow-up of chronic patients, we evaluated performance of French private practice general practitioners (GPs) practicing in multi-professional group practices (MGP), compared to their peers practicing outside MGP, regarding chronic care management during rst Covid-19 lockdown in spring 2020.
The cross-sectional web questionnaire of 1,191 GPs took place in April 2020. We exploit self-reported data on: 1) frequency of consultations for chronic patients during lockdown compared to their typical week before the pandemic, along with 2) GPs proactive behaviour when contacting their chronic patients. We use probit and seemingly unrelated probit models (adjusted for endogeneity of choice of engagement in MGP) to test whether GPs in MGP had signicantly dierent responses to the Covid-19 crisis.
We nd that GPs in MGP were less likely to experience a drop in consultations related to complications of chronic diseases. They were also more proactive to contact their chronic patients.
Quick policy response is needed to alleviate diculties encountered by GP practicing outside MGPs. Results advocate for further development of integrated care in the long run.
The growth incidence curve of Ravallion and Chen (2003) is based on the quantile function. Its distribution-free estimator behaves erratically with usual sample sizes leading to problems in the tails. We propose a series of parametric models in a Bayesian framework. A first solution consists in modelling the underlying income distribution using simple densities for which the quantile function has a closed analytical form. This solution is extended by considering a mixture model for the underlying income distribution. However in this case, the quantile function is semi-explicit and has to be evaluated numerically. The alternative solution consists in adjusting directly a functional form for the Lorenz curve and deriving its first order derivative to find the corresponding quantile function. We compare these models first by Monte Carlo simulations and second by using UK data from the Family Expenditure Survey where we devote a particular attention to the analysis of subgroups.
We investigate the effect of changing ENSO patterns on global commodity prices, including energy, metals/minerals and agriculture real commodity price subsets, while controlling for global economic output and interest rate via a global factor local projections (GFALP) model. We study the responses to climate shocks using a nonlinear multivariate model to assess differential effects across ENSO climate regimes. We find that commodity inflation is reactive to El Niño and La Niña events, but that this sensitivity can occur either in the short-or long-term depending on the commodity under investigation. For commodities in agriculture, we uncover an asymmetric influence of El Niño and La Niña shocks. More central banks are questioning whether climate change is part of their mission to stabilize prices. Our results indicate the existence of a direct link between weather anomalies and commodity inflation, one that should be integrated into the central banks' inflation targeting framework.
We study zero-sum repeated games where the minimizing player has to pay a certain cost each time he changes his action. Our contribution is twofold. First, we show that the value of the game exists in stationary strategies, depending solely on the previous action of the minimizing player, not the entire history. We provide a full characterization of the value and the optimal strategies. The strategies exhibit a robustness property and typically do not change with a small perturbation of the switching costs. Second, we consider a case where the minimizing player is limited to playing simpler strategies that are completely history-independent. Here too, we provide a full characterization of the (minimax) value and the strategies for obtaining it. Moreover, we present several bounds on the loss due to this limitation.
We study whether fiscal policies, especially public debt, can help to curb the macroeconomic and health consequences of epidemics. Our approach is based on three main features: we introduce the dynamics of epidemics in an overlapping generations model to take into account that old people are more vulnerable; people are more easily infected when pollution is high; public spending and public debt can be used to tackle the effects of epidemics. We show that fiscal policies can promote the convergence to a stable steady state with no epidemics. When public policies are not able to permanently eradicate the epidemic, public debt and income transfers could reduce the number of infected people and increase capital and GDP per capita. As a prerequisite, pollution intensity should not be too high. Finally, we define a household subsidy policy which eliminates income and welfare inequalities between healthy and infected individuals.
Government fiscal actions influence forward-looking private agents' current and future decisions, which, in turn, impact fiscal performance. This paper highlights this expectation channel with a Barro-type endogenous growth model where an impatient government finances growth-enhancing spending through income taxes and public debt. Fiscal and macroeconomic outcomes emerge from the interplay of households and policymakers' preferences for public expenditure and private consumption. I find that the government's maximizing its own utility and facing an endogenous interest spread are sufficient ingredients to yield multiple equilibria, independently of the government's policy intentions. The economy almost always heads to the high public spending equilibrium, emphasizing the importance of fiscal institutions to tame government impatience and bolster fiscal credibility.
This paper examines a novel negative impact of trade tariffs and the costs they induce by documenting how protectionism reversed the long-term improvements in education and the fertility transition that were well under way in late 19th-century France. The Méline tariff, a tariff on cereals introduced in 1892, was a major protectionist shock that shifted relative prices in favor of agriculture and away from industry. In a context in which the latter was more intensive in skills than agriculture, the tariff reduced the relative return to education, which in turn affected parents' decisions about the quantity and quality of children. We use regional differences in the importance of cereal production in the local economy to estimate the impact of the tariff. Our findings indicate that the tariff reduced enrolment in primary education and increased birth rates and fertility. The magnitude of these effects was substantial, with the tariff offsetting the increasing trend in enrolment rates and the decreasing one in birth rates by a decade.
In many societies, parents are involved in selecting a spouse for their child, and integrate this with decisions about migration and educational investment. What type of spouse do parents want for their children? We estimate parents' spousal preferences based on survey choices between random profiles. Preference data are elicited from parents or other relatives who actively search for a spouse on behalf of their adult child in Kunming, China. Economic variables (income and real estate ownership) are important for the choice of sons-in-law, but not daughters-in-law. Education is valued on both sides. We simulate marriage outcomes based on preferences for age and education and compare them with marriage patterns in the general population. Homogamy by education can be explained by parental preferences, but not by age: parents prefer younger wives, yet most couples are the same age. Additionally collected preference data from students can explain age distributions. Survey data from parents suggest that while they prefer younger wives, they also accept wives of the same age. Overall, marriage markets have a likely positive influence on education investments for both boys and girls.
We study the effect of legalization of same-sex marriage on coming out in the United States. We overcome data limitations by inferring coming out decisions through a revealed preference mechanism. We exploit data on enrollment in seminary studies for the Catholic priesthood, hypothesizing that Catholic priests' vow of celibacy may lead gay men to self-select as a way to avoid a heterosexual lifestyle. Using a differencesin-differences design that exploits variation in the timing of legalization across states, we find that city-level enrollment in priestly studies fell by about 15% exclusively in states adopting the reform. The celibacy norm appears to be driving our results, since we find no effect on enrollment in deacon or lay ministry studies that do not require celibacy. We also find that coming out decisions, as inferred through enrollment in priestly studies, are primarily affected by the presence of gay communities and by prevailing social attitudes toward gays. We explain our findings with a stylized model of lifestyle choice.
In this paper we analyze how growing income/wealth inequality and the functional income distribution inequality have contributed to the sustained low potential growth observed in the industrialized economies during the last two decades, a period that includes the Great Recession (GR). Growing inequality may constitute a drawback for the recovery of these economies, especially after the Great Pandemic (GP). To this aim, we modify the semi-structural model originally proposed by Holston, Laubach and William, by considering the effects of several types of inequalities. We jointly estimate potential growth and the natural interest rates. We show that the latter can substantially modify the time path of the real interest rate that prevails when economies are at full strength and inflation is stable.
This paper estimates trade barriers in government procurement, a market that accounts for 12% of world GDP. Using data from inter-country input-output tables in a gravity model, we find that home bias in government procurement is significantly higher than in trade between firms. However, this difference has been shrinking over time. Results also show that trade agreements with provisions on government procurement increase cross-border flows of services, whereas the effect on goods is small and not different from that in private markets. Provisions containing transparency and procedural requirements drive the liberalizing effect of trade agreements.
Using longitudinal data from the German SocioEconomic Panel, we analyze the effects of exposure to trade on the fertility and marital behavior of German workers. We find that individuals working in sectors that were more affected by import competition from Eastern Europe and suffered worse labor market outcomes were less likely to have children. In contrast, workers in sectors that benefited from increased exports had better employment prospects and higher fertility. These effects are driven by low-educated and married men, and reflect changes in the likelihood of having any child (extensive margin). While among workers exposed to import competition there is evidence of some fertility postponement, we find a significant reduction of completed fertility. There is instead little evidence of any significant effect on marital behavior.
There is strong evidence that national leaders matter for the performance of their nations, but little is known about what drives the direction of their effects. I assess how national leaders' quality of governance, measured by five indicators, varies with their career and education. Using text analysis and a sample of one thousand national leaders between 1932 and 2010, I identify five types of rulers: military leaders, academics, high-level politicians, low-level politicians and lawyers. Military leaders tend to be associated with a decrease in the quality of governance, whereas politicians who have held visible offices before taking power perform better. National leaders with a law background, as well as academics, can have negative effects depending on the political regime they run and on the choice of performance indicator. This highlights the heterogeneity behind the positive effect of holding a university degree, often used as a proxy for politicians' quality.
How will structural change unfold beyond the rise of services? Motivated by the observed dynamics within the service sector we propose a model of structural change in which productivity is endogenous and output is produced with two intermediate substitutable capital goods. In the progressive sector the accumulation of knowledge leads to an unbounded increase in TFP, as sector becoming asymptotically dominant. We are then able to recover the increasing shares of workers, the increasing real and nominal shares of the output observed in progressive service and IT sectors in the US. Interestingly, the economy follows a growth path converging to a particular level of wealth that depends on the initial price of capital and knowledge. As a consequence, countries with the same fundamentals but lower initial wealth will be characterized by lower asymptotic wealth.
A central idea in the institutions and development literature is whether the executive is adequately checked by the legislature and judiciary (North, 1990; Acemoglu et al., 2001; La Porta et al., 2004). This paper provides plausibly causal evidence on how increased constraints on the executive, through removal of Presidential discretion in judicial appointments, impacts judicial decision-making. In particular, we find that when the judge selection procedure in Pakistan changed, from the President appointing judges to appointments by judge peers, rulings in favor of the government decreased significantly and the quality of judicial decisions improved. The age structure of judges at the time of the reform and the mandatory retirement age law provide us with an exogenous source of variation in the implementation of the selection reform. We test for and provide evidence against potential threats to identification and alternative explanations for our findings. The analysis of mechanisms reveals that our results are explained by rulings in politically salient cases and by “patronage” judges who hold political office prior to their appointments. According to our estimates, Presidential appointment of judges results in additional land expropriations by the government worth 0.14 percent of GDP every year.
Although it is recognized that parental time is a strong determinant of child development, little is known about heterogeneity across the effects of parental time. Using the Longitudinal Survey of Australian Children, I model the cognitive and socio-emotional skills production functions for children born in 1999-2000, from 4 to 11 years old, using, among others, a cumulative value-added and a generalized method of moments model. I find that the effect on children's verbal and socioemotional skills of time spent on educational activities with the father is smaller than that with the mother or both parents together. For socio-emotional skills, this difference seems to be driven by fathers who spend little time with their children.
This study investigated elements affecting the ability to achieve optimal health (health capability) in people living in the rural area of Niakhar, Senegal, using data from the 12356 ANRS AmBASS survey. A structural equation modelling (SEM) strategy was used to develop a multidimensional and dynamic health capability model (Ruger, 2010) that allowed the analysis of determinants of health to be extended beyond the usual one-way study between determinants and health status found in the literature. Three factors (dimensions) were identified: 1) access to local healthcare services, 2) participation in decisionmaking, and 3) current self-reported health status. The model analyzed interactions between these dimensions as well as the dimensions' relationships with other demographic, psychosocial and economic variables (household size and resources, age, gender, education, marital status, intrinsic motivation, etc.) Results reveal a much greater diversity of variables associated with shortfalls in the various dimensions of health capability than what would have appeared had a standard unidimensional model been used. This SEM-based strategy could be an attractive alternative to traditional approaches to measure determinants of health and provide valuable empirical results for policy-makers.
Higher uncertainty about government spending generates a persistent decline in the economic activity in the Euro Area. This paper emphasizes the transmission channels explaining this empirical fact. First, a Stochastic Volatility model is estimated on European government consumption to build a measure of government spending uncertainty. Plugging this measure into a SVAR model, we stress that government spending uncertainty shocks have recessionary, persistent and humped-shaped effects. Second, we develop a New Keynesian model with financial frictions applying to a portfolio of equity and long-term government bonds. We argue that a portfolio effect-resulting from the imperfect substitutability among both assets-acts as a critical amplifier of the usual transmission channels.
We analyze the integration of intermittent renewables-based technologies into an electricity mix comprising of conventional energy. Intermittency is modeled by a contingent electricity market and we introduce demand-side flexibility through the retailing structure. Retailers propose diversified electricity contracts at different prices allowing consumers to choose their optimal electricity consumption. These contracts are modeled by a set of state-contingent electricity delivery contracts. We show existence and uniqueness of a competitive equilibrium of the contingent wholesale and retail markets. We provide a welfare analysis and only obtain constraint efficiency due to a limited number of delivery contracts. Finally, we discuss the conditions under which changing the set of delivery contracts improves penetration of renewables and increases welfare. This provides useful policy insights for managing intermittency and achieving renewable capacity objectives.
We revisit fertility analysis in Tunisia by examining family interference in birth control through: woman’s marriage age, post-marriage delay in the first use of contraception, past and current contraceptive use, and choice of the birth control methods.
Using data from the 2001 PAP-FAM Tunisian survey, we find that the significant effects of covariates arise and vanish across stage-specific equations as women progress in their lifecycle. In Tunisia, family links and socio-cultural environment appear to greatly shape fertility regulation in the direction of higher fertility. This calls for more intensive involvement of the extended families in family planning policies. This also suggests that the resurgence of traditionalist politico-religious movements, often associated with youth radicalization, may affect future fertility in Tunisia through an increase in family influences on birth control by married women.
Even though much has been learned about the new pathogen SARS-CoV-2 since the beginning of the COVID-19 pandemic, a lot of uncertainty remains. In this paper we argue that what is important to know under uncertainty is whether harm accelerates and whether health policies achieve deceleration of harm. For this, we need to see cases in relation to diagnostic effort and not to look at indicators based on cases only, such as a number of widely used epidemiological indicators, including the reproduction number, do. To do so overlooks a crucial dimension, namely the fact that the best we can know about cases will depend on some welldefined strategy of diagnostic effort, such as testing in the case of COVID-19. We will present a newly developed indicator to observe harm, the acceleration index, which is essentially an elasticity of cases in relation to tests. We will discuss what efficiency of testing means and propose that the corresponding health policy goal should be to find ever fewer cases with an ever-greater diagnostic effort. Easy and low-threshold testing will also be a means to give back people’s sovereignty to lead their life in an “open” as opposed to “locked-down” society.
Uprising in China, the global COVID-19 epidemic soon started to spread out in Europe. As no medical treatment was available, it became urgent to design optimal non-pharmaceutical policies. With the help of a SIR model, we contrast two policies, one based on herd immunity (adopted by Sweden and the Netherlands), the other based on ICU capacity shortage. Both policies led to the danger of a second wave. Policy efficiency corresponds to the absence or limitation of a second wave. The aim of the paper is to measure the efficiency of these policies using statistical models and data. As a measure of efficiency, we propose the ratio of the size of two observed waves using a double sigmoid model coming from the biological growth literature. The Oxford data set provides a policy severity index together with observed number of cases and deaths. This severity index is used to illustrate the key features of national policies for ten European countries and to help for statistical inference. We estimate basic reproduction numbers, identify key moments of the epidemic and provide an instrument for comparing the two reported waves between January and October 2020. We reached the following conclusions. With a soft but long lasting policy, Sweden managed to master the first wave for cases thanks to a low R 0 , but at the cost of a large number of deaths compared to other Nordic countries and Denmark is taken as an example. We predict the failure of herd immunity policy for the Netherlands. We could not identify a clear sanitary policy for large European countries. What we observed was a lack of control for observed cases, but not for deaths.
In this paper, I use a pseudo-panel approach with data from the European Union Labour Force Survey to study the impact of paternity leave policies on mothers' employment in ten countries. Using a dynamic Difference-inDifference strategy, I show that paternity leave increased mothers' employment rate by up to 17% in the long run, and average hours worked by 2 to 4%. There is substantial heterogeneity across countries in the effect of paternity leave policies. The impact on employment rates is positive and significant in eight of the ten countries of the sample, while the impact on hours worked can be either positive or negative. I find no evidence that the reforms had any impact on Greece or Portugal.
We provide evidence on the impact of Covid-19 restriction policies on conflicts worldwide. We combine daily information on conflict events and government policy responses to limit the spread of coronavirus to study how demonstrations and violent events vary following shutdown policies. We use the staggered implementation of restriction policies across countries to identify the dynamic effects in an event study framework. Our results show that imposing a nationwide shutdown reduces the number of demonstrations, which suggests that public demonstrations are hampered by the rising cost of participation. However, the reduction is short-lived, as the number of demonstrations are back to their pre-restriction levels in two months. In contrast, we observe that the purported increase in mobilization or coordination costs, following the imposition of Covid-19 restrictions, has no impact on violent events that involve organized armed groups. Instead, we find that the number of events, on average, increase slightly following the implementation of the restriction policies. The rise in violent events is most prominent in poorer countries, with higher levels of polarization, and in authoritarian countries. We discuss the potential channels that can explain this heterogeneity.
In the spirit of Blackwell (1951), we analyze how two fundamental mistakes in information processing-incorrect beliefs about the world and misperception of information-affect the expected utility ranking of information experiments. We explore their individual and combined influence on welfare and provide necessary and sufficient conditions when mistakes alter and possibly reverse the ranking of information experiments. Both mistakes by themselves reduce welfare in a model where payoff relevant actions also generate informative signals. This is true for naive decisionmakers, unaware of any errors, as well as for sophisticated decision-makers, who account for the possibility of mistakes. However, mistakes can interact in non-obvious ways and an agent might be better off suffering from both, rather than just one. We provide a characterization when such positive interactions are possible. Surprisingly, this holds true only for naive decision-makers and thus naivete can be beneficial. We discuss implications for information acquisition and avoidance, welfare-improving belief manipulation, and policy interventions in general.
This paper describes an empiric study of aggregation and deliberation used during citizens' workshops for the preference elicitation of 20 different ecosystem services (ESs) delivered by the Palavas coastal lagoons located on the shore of the Mediterranean Sea close to Montpellier (S. France). The impact of deliberation for the preference elicitation of 20 different ecosystem services (ESs) was studied by gathering and aggregating individual preferences before deliberation that were compared to the collective aggregation after deliberation. The same aggregation rules were used before and after deliberation and we compared two different aggregation methods, i.e. Rapid Ecosystem Services Participatory Appraisal (RESPA) and Majority Judgement (MJ). RESPA had been specifically tested for ESs, while MJ evaluates the merit of each item, an ES in our case, in a predefined ordinal scale of judgment. The impact of deliberation was strongest for the RESPA method. This new information acquired from application of social choice theory is particularly useful for ecological economics studying ES, and more practically for the development of deliberative approaches for public policies.
Entrepreneurship, growth and total factor productivity are larger when there is a financial bubble. We explain these facts using a growth model with financial bubbles in which individuals face heterogeneous wages and returns on productive investment. The heterogeneity in the return of in- vestment separates individuals between savers and entrepreneurs. Savers buy financial assets, which are deposits or a financial bubble. Entrepreneurs incur in a start-up cost and borrow to invest in productive capital. The bubble provides liquidities to credit-constrained entrepreneurs. These liquidities increase investment and entrepreneurship when the start- up cost is large enough, which explains that growth and entrepreneurship can be larger with bubbles. Finally, productivity can be larger when the bubble further increases the investment of more productive entrepreneurs. This can occur when the return of investment is correlated with wages.
Over the last half century, violent conflicts between ethno-religious organizations and states have shaped the political and economic development context in developing countries. However, global empirical evidence on the dynamic and strategic underpinnings of these phenomena is lacking. Here, we investigate the dynamic violent relationships between the organizations that represent minorities at risk and the governments in Middle-Eastern and North African countries. Our estimates of dynamic panel data models of discrete strategic responses reveal dampened cycles of violence between states and insurgent politico-ethnic organizations due to violent mutual responses. However, such cycles are absent when the organizations target civilians instead, which is more likely after an insurgency spell. Finally, we provide an original game-theoretical interpretative framework for our results, which allows us to identify, on average and under sensible restrictions, the Stag Hunt game as an appropriate representation of the (possibly reduced-form) general strategic situations that link states and minority organizations in MENA.This is at odds with the frequent use of the prisoner's dilemma setting in the literature, or of other ad hoc strategic hypotheses, to analyze conflicts.
We estimate the demand for money for monetary aggregates M1 and M2, and cash in Algeria over the period 1979-2019, and study its long-run stability. We show that the transaction motive is significant for all three aggregates, especially for the demand for cash, reflecting the weight of informal economy “practices”. The elasticity of the scale variable is very close to unity for M2 and M1, and even equal to unity for cash demand (1.006). The elasticity of inflation is also significant for all three aggregates, although its level is higher in the case of cash demand (-6.474). Despite the persistence of certain financial repression mechanisms, interest rate elasticity is significant for all three aggregates, but higher for M1 and cash. The same observation is made for elasticity of the exchange rate, reflecting the effect of monetary substitution, especially for M1 and cash. Finally, our study concludes that the demand for money in terms of M1 remains stable, the same observation being confirmed for the M2 aggregate. However, the demand for fiat currency proves not to be stable. The consequences for the optimal design of monetary policy in Algeria are clearly stated.
This paper is the last part of a trilogy on the theory and history of entrepreneurship in Austrian school of economics. The triptych ends with contemporary members by comparing Israel Kirzner and Murray Rothbard. The migration of the Austrian school induced a new assessment of Austrian traits in a new setting. While we do not focus on the history of the Austrian school in America as such, we will stress how Kirzner focused his view of entrepreneurship on the concepts of alertness, discovery by opportunity and the equilibrating action of the entrepreneur – while Rothbard’s contribution was more ideologically engaged.
Do households facing an interval of prices rather than a simple price alter the results of poverty analyses? To address this question, we exploit a unique dataset from Niger in which agropastoral households provide the minimum and maximum prices they paid for each consumed product in each season. We estimate poverty measures based on this price information using several absolute poverty line methodologies. Prices are used for valuing household consumption bundles, estimating household-specific price indices, valuing minimal calorie requirements, and extrapolating the link between food poverty and consumption.
The results for Niger show statistically significant differences in the estimated chronic and dynamic poverties for these approaches, especially for international poverty comparisons and seasonal transient poverty monitoring. Specifically, using minimum and maximum prices generates gaps in the estimated poverty rates for Nigerien agropastoral households that exceed regional poverty disparities, which implies that regional targeting priorities in poverty alleviation policies would be reversed if these alternative prices are utilized.
This result suggests that typically estimated poverty statistics, which assume that each household, or even cluster, faces a unique price for each product in a given period, may be less accurate for policy monitoring than generally believed.
A large literature characterizes urbanisation as the result of productivity growth attracting rural workers to cities. We incorporate economic geography elements into a growth model and suggest that causation runs the other way: when rural workers move to cities, the resulting urbanisation produces technological change and productivity growth. Urban density leads to knowledge exchange and innovation, thus creating a positive feedback loop between city size and productivity that sets off sustained economic growth. The model is consistent with the fact that urbanisation rates in Western Europe, and notably in England, reached unprecedented levels by the mid-18 th century, the eve of the Industrial Revolution.