PPF (Public provident fund) holds an iconic status as far as saving/investment options are concerned but in recent years interest rates on PPF investments have been declining steadily latest interest rates on PPF is 7.9 % for Q1 2017-2018. Interest rates on PPF now trail yields on government securities and hence will always stay in line with interest rates on other saving rates in market.
The graph below shows how interest rates have moved for your