A nationwide census was taken every three years during the Yi dynasty in Korea, producing thousands of census registers (hojŏk) for each county. The present study uses the 1606 and 1630 registers for Sanŭm County to study the extent and direction of social mobility in the county during the twenty-four-year period between the two registers.

Analysis of Sanŭm County census registers shows that the overall direction of social mobility in the county between 1606 and 1630 was downward, though a small percentage of households was recorded as having undergone upward mobility during the period. Some of the upward mobility may be attributed to government policies enacted during the Hideyoshi invasions of Korea to allow citizens to purchase higher status with grain contributions. The study suggests that the rigid stratification of Yi-dynasty society could no longer be maintained following the Hideyoshi invasions, and that social mobility was predominantly, though not exclusively, downward.