Usually the benchmark rate of interest in any market is the risk free rate of return an investor can get by investing hisher money in any instrument, that is the safets of all investments.Usually the risk free returns are the yields one gets in government bonds since it is assumed that government is unlikely to go back on its commitment to pay interest to a holder of bonds it has issued. In India the yield that one gets by investing in the government bonds (gilts) of 10-year maturity is the benchmark rate. Every year the government issues a new gilt of 10-year maturity because after one year as the maturity date comes closer, a 10-year gilt would have a residual life of nine more years. And the yield on the same gilt can not reflect the 10-year yield. Benchmark yield is available on the RBI's website.