Since the mid-1970s, historians of the West have emphasized the World War II years as a major watershed, as a region experienced enormous social and economic change, and became the pacesetter for societal evolution. The population soared, especially in metropolitan areas, as a result of massive expansion of the manufacture of airplanes, ships and munitions and of military and Naval training facilities. California upgraded universities to world-class status, intensified scientific research, and expanded infrastructure. After the war millions more migrated using the GI Bill to buy suburban homes, many of them recalling rewarding wartime experience in military training facilities. The region had always been more democratic with greater racial and gender equality, and continued as a national pacesetter in modernization. New problems emerged, especially environmental issues where westerners took the lead in areas such as the allocation of scarce water resources as well as dealing with smog and air pollution. More recently historians have looked at nuances, pointing out that some of the trends began before 1941.