TWII or Taiwan Weighted also known as The Taiwan TWSE 50 Index was started on October 29, 2002. The collaboration of Taiwan Stock Exchange Corporation (TWSE) and FTSE International Limited created the first tradable index for the Taiwan stock market. It keeps track of the top 50 companies by total market capitalization.

The index calculation is based on the FTSE’s free float methodology. It ensures the weights within the index reflect the market capitalization available for investment. The index is managed by the TWSE Taiwan Index Series Advisory Committee, an independent committee.

The base value was set at 5,000 on April 30, 2002. The index is reviewed by the committee quarterly in January, April, July and October every year and constituent changes are made on the next trading day following the third Friday of the same month.