Debates about the sluggish recovery in output, the low growth in labor productivity, and the actual level of slack in the U.S. economy are common within policy circles (see, for example, this speech by Fed Chair Janet Yellen and previous macroblog posts—here and here). One of the defining features of the recovery from the Great Recession has been the rise in the number of people employed part-time. As reported by the U.S. Bureau of Labor Statistics, roughly 10 percent more people are working part-time in September 2014 than before the recession. Part-time workers generally earn less per hour than full-time workers, so lower hours and lower per-hour earnings both contribute to their lower incomes. Despite those differences in wage levels, less is known about wage growth of part-time relative to full-time workers. Has wage growth been different? Has wage inequality increased across the two groups of workers?
To find out, we employ data from the Survey of Income and Program Participation (SIPP) to analyze the wage growth of part-time and full-time workers. The SIPP is a longitudinal survey designed to be representative of the U.S. labor force. It is constructed as a sequence of panels of households who are interviewed for three to five years. Designed and maintained by the U.S. Census Bureau, the first panel began in 1984, and the most recent panel started in 2008. Households are interviewed every four months during the time they remain in the sample, providing information on work experience (employment, hours, earnings, occupation, and industry, among other variables) for the months between interviews.
The 2008 SIPP panel data that we use cover the period from August 2008 to April 2013. We restrict the analysis to hourly workers, a group representing roughly half of all employed in the 2008 panel. The reason we focus on this group is that they provide the cleanest measure of the price of labor: a wage rate for each hour they work. The remainder of workers—those compensated with a monthly or annual salary—do not report such a measure, and it needs to be inferred from their responses about total earnings and total hours worked. Because hours reported in the SIPP include much missing data and are sometimes inaccurate, we discard salaried workers. We also exclude anyone whose wages or hours information was allocated or imputed and anyone at the top or bottom of the wage distribution.
We divide the sample into two groups: those whose usual hours are fewer than 35 hours a week (part-time workers) and those who usually work 35 hours or more per week (full-time workers). We then compare the distribution of wage growth for each group and compute the median wage growth rate. To eliminate short-term fluctuations and seasonal effects, we compute median hourly wage growth rates over a three year period, expressed as an annual rate. Since the data start from August 2008, our series for the wage growth rate starts from August 2011.
Chart 1 shows the median wage growth rate of individuals over time. During the recovery, the median growth rate of full-time workers has been higher than that of part-time workers. In particular, wage declines were more common among part-time workers.
To further analyze the wage growth pattern of full-time and part-time workers, we subdivide the sample by education. Chart 2 plots the median wage growth rates for those with at least a bachelor's degree and those with some college or less. The median wage growth rates for full-time workers are larger than for part-time workers within each education group and highest for college graduates working full-time. Also apparent is that the weak wage growth of part-time workers is significantly influenced by the sluggish wage growth among those with less than a bachelor's degree.
Overall, we find that part-time workers as a group appear to experiencing a lower average wage growth rate than full-time workers during the recovery from the Great Recession. Education matters for wage growth, but the pattern of lower wage growth for part-time workers persists for people with broadly similar educational attainment.
By Lei Fang, research economist and assistant policy adviser, and
Pedro Silos, research economist and associate policy adviser, both in the Atlanta Fed's research department