The quarterly price index compiled by the Urban Redevelopment Authority, Displayed that prices of private residential properties rose by 0.6 per cent in the third quarter of 2012; whereas the price increase was only 0.4 per cent in the second quarter of 2012. A similar trend was spotted in the National University of Singapore (NUS) Singapore Residential Price Index (SRPI), developed by the Institution of Real Estate Studies. Unlike the price index of URA, SRPI is a monthly index that only looks at the price movements of private non-landed residential properties. Based on a study by a NUS don, Assoc Prof Tilak Abeysinghe, Singapore's real estate prices have been raising above the affordable level of a 4 per cent increase annually. This number is arrived at based on the lifetime incomes of Singaporeans.