Mortgage rates dipped Wednesday as concerns about riots in Greece and debt problems for other European countries caused a large decline in global stock markets. Investors shifted funds to safer assets, which helped mortgage-backed securities. Today’s economic data had little impact on markets. March Pending Home Sales rose 5.3% from February, aided by homebuyer tax credits. The index is a leading indicator for the housing sector. Contracts had to be signed by April 30 to qualify for the credit, so May activity will be watched closely by analysts. The Institute for Supply Management services index was unchanged for April. A small increase had been expected. No other data will be released today.