We develop new evidence on the cumulative earnings losses associated with job displacement, drawing on longitudinal Social Security records for U.S. workers from 1974 to 2008. In present value terms, men lose an average of 1.4 years of re-displacement earnings if displaced in mass layoff events that occur when the national unemployment rate is below 6 percent. They lose a staggering 2.8 years of pre-displacement earnings if displaced when the unemployment rate exceeds 8 percent. These results reflect discounting at a 5% annual rate over 20 years after displacement. We also document large cyclical movements in the incidence of job loss and job displacement and present evidence on how worker anxieties about job loss, wage cuts and job opportunities respond to contemporaneous economic conditions. Finally, we confront leading models of unemployment fluctuations with evidence on the present value earnings losses associated with job displacement. The model of Mortensen and Pissarides (1994) extended to include search on the job generates present value losses less than one-fourth as large as observed losses. Moreover, present value losses in the model vary little with aggregate conditions at the time of displacement, unlike the pattern in the data.