The one child policy, was an official program initiated in the late 1970s and early '80s by the central government of China, the purpose of it being to limit the great majority of family units in the country to one child each. The rationale for implementing the policy was to reduce the growth rate of China's enormous population.
The puritans were forced to leave and flee because of their religious beliefs.
The Louisiana Purchase changed the US because it doubled the size of the then US. Thomas Jefferson was eager for Lewis and Clark to explore the West because he wanted to find new places for the colonist to live and people to settle there before anyone else did.
I believe it's called checks and balances.
