The fastest-growing segments of America’s job market — by far — are temporary and part-time employment. According to the Bureau of Labor Statistics, the number of US part-time employees hit a record high of 28 million. Temporary employment has jumped 50% since the depths of the financial crisis. This “ephemeral workforce” phenomenon isn’t just American; the UK has also set records in the contingently employed. Something profoundly structural is going on. Even healthier economic growth won’t make it go away.