In the US, the MBA Weekly Mortgage Application Survey is a comprehensive overview of the nationwide mortgage market and covers all types of mortgage originators, including commercial banks, thrift institutions and mortgage banking companies. The entire market is represented by the Market Index which covers all mortgage applications during the week, whether for a purchase or to refinance.
A higher than expected figure should be seen as positive (bullish) for the USD while a lower than expected figure should be seen as negative (bearish) for the USD.