18 indices are calculated in 3 groups on the ISE Government Debt Securities (DBS) markets where treasury bills and government bonds are traded:
GDS price indices
GDS performance indices
GDS portfolio performance indices
The prices of bonds and bills change for two reasons: change in market interest rate and price increase towards the end of the term .
While GDS price indices measure the price change caused by the variation in market interest rate, GDS performance and portfolio performance indices measure the yield earned by the investor with reference to both the variation in interest rate and the reduction in the number of days to maturity.
GDS indices are calculated on each trading day from the weighted average prices of the executed trades of discounted securities on the Bonds and Bills Market Outright Purchases and Sales Market.