People working part-time who would prefer to be working full-time comprise a large group in the United States. These people may be referred to as working “part time for economic reasons,” “involuntarily part-time,” or “underemployed.”1 Since 1994, there has been an average of 5.4 million underemployed workers in the United States, rising to more than 9 million during the 2008–2009 Great Recession and to more than 10 million in the 2020 recession caused by the SARS-CoV-2 (COVID-19) pandemic. In this Commentary, we study the behavior of US underemployment during recent business cycles. In particular, we focus on the ... (full story)