"This represents about 1.4 million additional individuals who are stuck in part-time jobs. These numbers imply that the level of IPT work is about 40 percent higher than would normally be expected at this point in the economic expansion," said the Federal Reserve. 

The question, then, is why. The Federal Reserve believes this is almost entirely because of what industries managed to thrive in the wake of the financial crisis. Some of the strongest recovery over the years has been in the leisure and hospitality sector and the education and health-services sector, both of which are known for high rates of part-time employment. Adding onto this is the rise of gig economy jobs like driving for Uber or doing odd jobs on Task Rabbit. Given that these are now major parts of the economy, the Federal Reserve does not believe this will change anytime soon. 

"The shift toward service industries with uneven work schedules and the rising importance of the gig economy appear to be long-term trends that are unlikely to reverse in the near future. As such, in the absence of public policies aimed directly at altering work schedules, it looks like higher rates of involuntary part-time work are here to stay," said the Federal Reserve.