JOEL - According to the 2006 Deseret News Church Almanac, Mormons make up about 72% of the population of Utah. I have seen other reports that puts it closer to 62%. Salt Lake county has about 50%, so there may actually be more non-Mormons living in Salt Lake City.
According to a 2001 study by Express Scripps, Utah ranks number 1 in antidepressant use; about 16% of the population.

TED - It has been said, "a small percentage of worthy priesthood holders were allowed to practice plural marriage." I believe this statement to be more accurate than not, however, what evidence is there of this being the case. Some critics say it was a higher percentage than small.

JOEL - I am not sure what kind of evidence you want. The exact number of households involved in polygamy is not known. But according to available information, what numbers are known vary according to what time period you look and the particular community. In some towns as little as 5% (South Weber) were involved and others as high as 40% (St George). It averages out to about 20 to 25% of all LDS adults(about 5% of the men) at the height of the practice(1850s), which would be about 1200 people (assuming all Utah residents were Mormon). In about 66% of the cases one man was married to only two women; about 20% were married to three women; and the rest to more than three.