No law, varying the compensation for the services of the Senators and Representatives, shall take effect, until an election of representatives shall have intervened.
This amendment is interesting. It is the last amendment passed, yet it was one of the first suggested. It was originally proposed in 1789. That was 227 years ago. It was only ratified in 1992, which was only 24 years ago. James Madison proposed it, yet somehow it took (according to wiki) 202 years, 7 months, and 12 days to ratify. Seven states ratified it by 1792 (almost half the states in the nation at that time). However, the ratification process seemed to lag just behind the increase of states, requiring it to need more and more states.
There are currently only 4 states that have never ratified it. Massachusetts, Mississippi, New York, and Pennsylvania. Not that they really need to – its already law.
It was a bit of a controversy when it finally became ratified, as Congress had never dealt with a 200 year old amendement. Some wanted it reviewed for validity. However the Supreme Court held that any amendment not given a ratification deadline can be ratified at any point.