When researching family history, a number of factors can be beneficial in assisting you. One of those factors is family size. Compared to the general population, the demographic patterns for Mormons have historically been different. Demographic areas in which Mormons, know known as Latter-day Saints, are particularly high tend to have higher than average family sizes. Utah is an example of this. Mormons make up approximately 70% of the population of Utah. Historically, the fertility rates in Utah have consistently been noted as being higher than the national average.
Today, the average Mormon family size tends to be around 4 children per family. Compared to the past, this is much smaller than early Mormon families; however, it is still approximately double the average family size of non-Mormon families. Historically, speaking Mormon families tended to have at least six children and it was not at all uncommon for families to have far more children than that. Families consisting of nine and ten children were not considered to be out of the ordinary in the least.
One of the reasons that family sizes seem to have decreased is the lessening emphasis on avoidance of birth control. Historically, it seems that there tended to be a strong emphasis on not using birth control; however, today the matter of whether to use birth control or not seems to be largely left up to couples to individually decide what is right for them.
Though the LDS now ex-communicates church members who practice plural marriage, this was not the case during much of the 19th century. While not all Mormon families practiced plural marriage during this time, there were some who did. As a result, this contributed in some cases to larger family sizes. It is difficult to know for certain how many Mormon families during the 19th century practiced plural marriages; however, estimates indicate that as many as 25% of families may have been polygamist households. When tracing family history it is important to note that not all plural marriages actually produced children, as some marriages were of a non-intimate nature and were considered to be ‘celestial’ marriages only. It is also important to note that while many families did live together in a large home, it was not uncommon in polygamous families for each wife and her children to have their own home, especially in families where it was financially feasible to do so.