The part-time labor market ratio is a high-quality slack indicator, often capturing weakness before a spike in the unemployment rate. An early warning sign. The part-time labor market ratio measures the number of people working part-time for non-economic reasons compared to economic reasons. Non-economic reasons mean voluntary part-time work (school, caregiving, lifestyle, etc.) Economic reasons mean involuntary part-time work (you want a full-time job but can't find one). The December labor market report showed a follow-through in this ratio declining, a signal that there's a rising number of people working part-time, not because they want to, but because they cannot get hired full-time.