I wish trends like the Flynn effect (rise in IQ in most of the world throughout the 20th century, including China [0], Japan and Korea [1]) had more concrete answers by now. AFAIK we still don't have any answers beyond conjectures. To me, having a better understanding of this is vital, because IQ is currently in decline in many developed countries, even when you account for immigration and demographic/race changes. Something in our environment is causing a reverse Flynn effect [2] [3], we don't know what it is, and not enough people seem to care.