Of 3,142 counties in the United States in 2013, Clay County ranked 3,137 in the longevity of female residents and 3,109 in the longevity of male residents. Males in Clay County lived an average of 68.6 years and females lived an average of 73.6 years compared to the national average for longevity of 76.5 for males and 81.2 for females. Moreover, the average longevity in Clay County declined by 0.4 years for males and  3.4 years for females between 1985 and 2013 compared to a national average for the same period of an increased life span of 5.5 years for men and 3.1 years for women. High rates of smoking and obesity and a low level of physical activity appear to be contributing factors to the lowered longevity for both sexes.
Question: How many years did it take for female longevity in Clay County to drop 3.4 years?
Answer: 28