BERWYN, Pa.--(BUSINESS WIRE)--According to the yearly sales tax rate study issued today by Vertex Inc., the leading provider of corporate tax solutions, the number of sales and use tax rate changes in the U.S. for year 2014 was 491, down from 2013 when there were 609 changes. State sales tax rates remained unchanged in 2014, and for the first half of 2015. However, there were 207 sales and use tax rate changes in just the first two quarters of 2015, up from 159 in the first six months of 2014.