I think the answer is increase because of the great depression
A grand jury returned indictments against seven of President Richard Nixon's closest aides in the Watergate affair. The special prosecutor appointed by Nixon and the defendants sought audio tapes of conversations recorded by Nixon in the Oval Office. Nixon asserted that he was immune from the subpoena claiming "executive privilege," which is the right to withhold information from other government branches to preserve confidential communications within the executive branch or to secure the national interest. Decided together with Nixon v. United States.
The World War II was the worst thing that has happened to the human kind. It was a war in which were included countries from all over the world. Millions of people lost their lives, be it soldiers or civilians, many of which only because they were belonging to certain ethnic or religious group. The winners in this war were the Allied Forces. Once they won it and put end to it, they started to try to reshape the world. This unfortunately led to another long lasting conflict between the two biggest powers, the United States and the Soviet Union. This put the world in a period of tensions and constant fear of another war, and that lasted for half a century. The losers in the war were restricted in many ways, especially in their military, and they started to focus on economic rebuilding and development, gradually transforming them into economic powerhouses.
It would be "historians" who are most likely to study written records, since geologists and archaeologists usually work instead with artifacts and fossils, to determine what happened in "prehistory".
