Not sure how you define dramatically, but this page (http://data.bls.gov/timeseries/LNS11300000) says that it dropped from a (local?) high of a little over 66% in January, 2007 to a (local?) low between 62 and 63% sometime in 2015, and is now rising a little. If you look at the page, be aware that the graph at the top is misleading because it doesn't start the Y-axis at 0.

And where did those number come from? Remember, there are lies, damn lies and statistics....