Answer based on context:

Tsakhiagiin Elbegdorj, as the chairman of the Democratic Party (Mongolia), co-led the Democratic Union Coalition to its first time historic victory in the Mongolian legislative election, 1996s winning 50 out of 76 parliamentary seats. Democratic Union Coalition of Democratic Party and Social Democratic Party (chairman Tsakhiagiin Elbegdorj) was in power in 1996-2000. Mendsaikhany Enkhsaikhan, election manager of Democratic Union Coalition worked as the Prime Minister from 7 July 1996 to 23 April 1998. In 1998, a clause in the constitution was removed that prohibited members of parliament to take cabinet responsibility. Thus on 23 April 1998, the Parliament elected (616) Elbegdorj, chairman of the Democratic Union Coalition and the Majority Group at the Parliament as the Prime Minister. Due to opposition MPRPs demand Elbegdorj lost confidence vote at the Parliament and was replaced by Janlavyn Narantsatsralt (Democratic Party) on 9 December 1998. Janlavyn Narantsatsralt worked as the Prime Minister for eight months until his resignation in July 1999. Rinchinnyamyn Amarjargal became Democratic Partys new chairman and served as the Prime Minister from 30 July 1999 to 26 July 2000.

How many years was the Democratic Union Coalition of Democratic Party and Social Democratic Party in power?
4