This paper measures the probability that an employed worker becomes unemployed and the probability that an unemployed worker finds a job. Using U.S. data from 1948 to 2007, the author finds that the job finding probability fluctuates significantly at business cycle frequencies, while the employment exit probability is relatively stable. The job finding probability accounts for three-quarters of the fluctuations in the unemployment rate since 1948, rising to 95% in the last two decades. The author argues that fluctuations in the job finding probability, not the employment exit probability, are the main drivers of unemployment fluctuations. This contradicts the conventional wisdom that recessions are characterized by high exit rates from employment. The author uses novel but simple measures of job finding and employment exit probabilities, based on two strong assumptions: workers neither enter nor exit the labor force, and all workers are ex ante identical. These measures rely on microeconomic data and show that the job finding probability is strongly procyclical, while the employment exit probability is acyclic. The author also explores what happens when these assumptions are relaxed, finding that the results remain largely unchanged. The author concludes that the job finding probability is the key factor in explaining fluctuations in the unemployment rate, and that the conventional wisdom based on research by Darby, Haltiwanger, and Plant, Blanchard and Diamond, and Davis and Haltiwanger has been misinterpreted. The author emphasizes the importance of time aggregation and heterogeneity in the analysis, arguing that changes in the composition of the unemployed population do not drive the results. The paper also highlights the importance of using publicly available data and the need for further research on the cyclicality of job finding and employment exit probabilities.This paper measures the probability that an employed worker becomes unemployed and the probability that an unemployed worker finds a job. Using U.S. data from 1948 to 2007, the author finds that the job finding probability fluctuates significantly at business cycle frequencies, while the employment exit probability is relatively stable. The job finding probability accounts for three-quarters of the fluctuations in the unemployment rate since 1948, rising to 95% in the last two decades. The author argues that fluctuations in the job finding probability, not the employment exit probability, are the main drivers of unemployment fluctuations. This contradicts the conventional wisdom that recessions are characterized by high exit rates from employment. The author uses novel but simple measures of job finding and employment exit probabilities, based on two strong assumptions: workers neither enter nor exit the labor force, and all workers are ex ante identical. These measures rely on microeconomic data and show that the job finding probability is strongly procyclical, while the employment exit probability is acyclic. The author also explores what happens when these assumptions are relaxed, finding that the results remain largely unchanged. The author concludes that the job finding probability is the key factor in explaining fluctuations in the unemployment rate, and that the conventional wisdom based on research by Darby, Haltiwanger, and Plant, Blanchard and Diamond, and Davis and Haltiwanger has been misinterpreted. The author emphasizes the importance of time aggregation and heterogeneity in the analysis, arguing that changes in the composition of the unemployed population do not drive the results. The paper also highlights the importance of using publicly available data and the need for further research on the cyclicality of job finding and employment exit probabilities.