Decreasing Gross Domestic Product

This csv has the United States Gross Domestic Product (GDP) from January 1, 1947 to October 1, 2014. Calculate how many times the GDP has decreased from one period to the next over this data series. Here is an example:

1947-01-01, 1934.5
1947-04-01, 1932.3
1947-07-01, 1930.3
1947-10-01, 1960.7

In 1947, the GDP decreased two times, once in the second quarter and again in the third quarter.