The ratio of the gross district domestic product (GDDP) of Chennai in current prices to the GDDP in constant 1999/2000 prices, both for 2005 and 2006 was used. This provided the price index over 1999/2000 to 2005/06. This ratio was applied to GDDP of Chennai for 2005/06 (in current prices) to arrive at the GDDP of Chennai for 2011/12 in current prices (as the contribution estimates are in current prices for 2011/12).