Long term yield on GIC portfolio

GIC reported a 10 year and 20 year yield on their portfolio of 7.4% and 7.2% respectively in USD. I wonder what the yield would have been, if converted to SGD. We know that the USD has depreciated significantly during this period.

I am encouraged by this statement: "GIC's real rate of return in excess of global inflation over the past 20 years -- its main benchmark -- was 3.9 percent as at end-March 2011, up from 3.8 percent at end-March 2010."

However, it might be better if the yield is converted to SGD and the real return is computed net of inflation in Singapore.