Has the marrying age of a man changed over the years? the united states bureau of the census takes a formal count of everyone in the u. s. every 10 years and has provided the following data that gives the median age of an american man at the time of his first marriage.. year1910192019301940195019601970198 019902000. median age25.124.624.324.322.822.823.224.7 26.126.8. . determine a ten-year period when the average rate of change is negative. a.1910 - 1920. b.1920 - 1930. c.1940 - 1950. d. all of the above