The Storting has always been "de jure" unicameral, but before a constitutional amendment in 2009 it was de facto bicameral. After an election, the Storting would elect a quarter of its membership to form the Lagting, a sort of "upper house" or revising chamber, with the remaining three-quarters forming the Odelsting or "lower house". The division was also used on very rare occasions in cases of impeachment. The original idea in 1814 was probably to have the Lagting act as an actual upper house, and the senior and more experienced members of the Storting were placed there. Later, however, the composition of the Lagting closely followed that of the Odelsting, so that there was very little that differentiated them, and the passage of a bill in the Lagting was mostly a formality.