文档介绍：EARNINGS INEQUALITY AND MOBILITY
IN THE UNITED STATES: EVIDENCE FROM
SOCIAL SECURITY DATA SINCE 1937∗
WOJCIECH KOPCZUK
EMMANUEL SAEZ
JAE SONG
This paper uses Social Security Administration longitudinal earnings micro
data since 1937 to analyze the evolution of inequality and mobility in the United
States. Annual earnings inequality is U-shaped, decreasing sharply up to 1953 and
increasing steadily afterward. Short-term earnings mobility measures are stable
over the full period except for a temporary surge during World War II. Virtually
all of the increase in the variance in annual (log) earnings since 1970 is due to
increase in the variance of permanent earnings (as opposed to transitory earnings).
Mobility at the top of the earnings distribution is stable and has not mitigated the
dramatic increase in annual earnings concentration since the 1970s. Long-term
mobility among all workers has increased since the 1950s but has slightly declined
among men. The decrease in the gender earnings gap and the resulting substantial
increase in upward mobility over a lifetime for women are the driving force behind
the increase in long-term mobility among all workers.
I. INTRODUCTION
Market economies are praised for creating macroeconomic
growth but blamed for the economic disparities among individuals
they generate. Economic inequality is often measured using high-
frequency economic es such as annual e. However,
market economies also generate substantial mobility in earnings
over a working lifetime. As a result, annual earnings inequal-
ity might substantially exaggerate the extent of true economic
disparity among individuals. To the extent that individuals can
smooth changes in earnings using savings and credit markets, in-
equality based on longer periods than a year is a better measure
∗We thank Tony Atkinson, Clair Brown, David Card, Jessica Guillory, Russ
Hudson, Jennifer Hunt, Markus Jantti, Alan Krueger, David Lee, Thomas
Lemieux,