Median fraction of stellar luminosity emitted in flares (FA), and standard deviation plotted against age. The values are grouped by T_eff, and presented on a log-log scale. The colors and shapes are the same as in Fig. 6. We calculated the shared energy detection threshold 3.31 × 10³² erg using the method described in Sect. 4.1 to derive FA with Eq. (8). FA is a useful measure of relative stellar activity as long as the flux portion of the quiescent star in the Kepler band is roughly constant. It is therefore more meaningful to compare FA across age than across T_eff.