In this thesis, I investigate the role of expectations in business cycles by studying three different kinds of expectations. First, I focus on a theoretical explanation of business cycles generated by changes in expectations which turn out to be self-fulfilling. This chapter improves a puzzle from the sunspot literature, thereby giving more evidence towards an interpretation of business cycles based on self-fulfilling prophecies. Second, I empirically analyze the propagation mechanisms of central bank announcements through changes in market participants’ beliefs. This chapter shows that credible announcements about future unconventional monetary policies can be used as a coordination device in a sovereign debt crisis framework. Third, I study a broader concept of expectations and investigate the predictive power of political climate on the pricing of sovereign risk. This chapter shows that political climate provides additional predictive power beyond the traditional determinants of sovereign bond spreads. In order to interrogate the role of expectations in business cycles from multiple angles, I use a variety of methodologies in this thesis, including theoretical and empirical analyses, web scraping, machine learning, and textual analysis. In addition, this thesis uses innovative data from the social media platform Twitter. Regardless of my methodology, all my results convey the same message: expectations matter, both for economic research and economically sound policy-making.