This is the latest chart from John Robertson and Ellyn Terry, published at the Atlanta Fed's macroblog. As the researchers say in their post, the data is pretty noisy, but it seems clear that something happened to part-time wage growth between 2011 and 2013 - after tracking pretty closely to full time wage growth over the last decade and a half, it pretty clearly detached in 2011.
In a previous post, Lei Fang and Pedro Silos at the Atlanta Fed broke down the median wage growth by education as well as time spent at work.
There's a pretty clear drop there for part-time workers without a college degree, that then stagnates just above 1% wage growth around mid-2012. Given that the inflation rate was 3% in 2012, these workers were effectively getting a pay cut.
There is some good news in the recent data, in that wages seem to be rising a bit more.
But there are still a lot of involuntary part-time workers feeling the sting even more thanks to wages that just won't budge.
Here's more from Robertson and Terry's post: "The SIPP data used by Fang and Silos ended in mid-2013. The more recent CPS data suggest that overall wage growth has picked up during the last year and that the wage growth gap has closed a bit, which are encouraging findings. But the wage growth of part-time workers, as a group, continues to lag well behind that of full-time workers. The relatively low wage growth of part-time workers heightens the importance of the fact that the number of people working part-time-especially involuntarily part-time-remains elevated."