Our primary approach for defining low-wage workers was to use the hourly wage at which a full-time worker would have annual earnings below poverty for a family of four. We calculated separate low-wage cutoff values for each calendar year the SIPP panel covered. We then classified a worker as "low-wage" if the worker's wage rate was less than the cutoff level in the calendar year when the wage rate was reported. Using federal poverty guidelines, and assuming a full-time worker works 2,080 hours per year, we set the low-wage cutoff at $7.50 in 1996, $7.72 in 1997, $7.91 in 1998, $8.03 in 1999, and $8.20 in 2000. We defined medium-wage workers as those with wage rates between one and two times the low-wage cutoff value and high-wage workers as those with wages more than twice the low-wage cutoff value.