It is pretty clear that the post-2008 U.S. labor market is such that it totally deranged the unemployment rate as a meaningful measure of labor market slack, and we now need to look at primate-age EPOP. But it also deranged prime-age EPOP—only not as badly:

Josh Bivens: Predicting Wage Growth with Measures of Labor Market Slack: It’s Complicated: "Why have wages grown so slowly in recent years despite relatively low unemployment rates? This puzzle has dominated economic commentary.... Since 2008, the share of adults between the ages of 25 and 54 who are employed (or the 'prime-age EPOP') has predicted wage growth better than the unemployment rate. But even the prime-age EPOP has done a poor job at predicting wage growth since 2008 compared with both its own predictive power pre-2008 and the predictive power of the unemployment rate in earlier periods...