Every April I get excited when at conference they announce the statistics for the previous year. Maybe it’s self-serving in a way to learn how the church has grown, and that it continues to grow. I have wondered what would happen if one year they reported a decline in membership. I imagine Latter-day Saints would freak out; it would go against their assumption that the growth of the kingdom correlates with numerical growth in overall membership. Or at least, it would challenge that assumption. The church just cannot decline in number, or something is disastrously wrong.

This year I decided to plug in the numbers myself and get a sense of the numerical tale of Mormon expansionism. Thanks to a trusty church almanac and some of my own digging, I was able to plot it all into a spreadsheet and run some numbers. Of course, church membership has grown rapidly in the latter half of the 20th century. But to get an idea of what that even means, I used a measurement that produced a very different-looking graph.

This measurement takes into account a 25-year span of raw numerical growth or decline. To explain, picture this. A ward of 100 persons in 1990 grows over a 10 year period. By 2000, the ward reports a membership of 200 persons. In effect, 50% of the ward in 2000 was not part of the congregation in 1990. Now, this does ignore many other factors, and it does not intend to address those, only to provide a picture of sustained growth trends over a longer period of time than just one year to the next. By no means does this measurement explain convert retention, baptisms, fluctuation in between years, etc. But I’m satisfied that it does point out key shifts in some growth trends.

The chart shows two curves. The blue shows how the percentages should appear in a situation where the population grows by the same number each year (e.g., each year the total membership increases by 500). The green curve shows the church’s actual growth rates. So, by looking at, say 1900, the value represents the percent of 1990’s membership that was not there 25 years prior. In raw math terms, the calculation is expressed as:

(Current Membership – Membership [25 yrs ago]) / Current Membership

Some insights include pointing out areas of sustained decline. Between 1855 and 1879, periods of decline brought the curve below the blue curve, meaning that the church grew less than a linear progression. In particular, 1855-57 experienced decline in church membership, and between 1858 and 1877 the church averaged a 4 percent growth rate. This points out not that the missionary work was not up to speed, but rather that in a 25-year span little by way of sustained population growth occurred. And with good reason. 1852, polygamy first officially sanctioned, takes a little while for a broader boom in population thanks to the practice; 1857-58, Mormon Reformation and Utah War; the first anti-polygamy law enacted in 1862, and missionary work in Mexico opens up in 1876. Once these historical events pan out, missionary work expands into Latin America, a critical mass of Mormons populate and settle the American west, and a steady program of international mission work gets put into place.

From 1922 to 1986, the systematic approach to world mission for Mormons receives heavy attention and becomes an institutionalized program which carries out consistent modes of proselytism. The graph demonstrates for this time period a large increase in raw numbers. We also see, after 1986, the curve move down, meaning that within 25-year chunks, the same level of sustained growth has not been maintained.

The rule of 70 says something, too, about what to expect in the coming years. This rule predicts how long it takes for a population to double by dividing 70 by the growth rate percentage. Using an average growth rate for the past 10 years of 2 percent, and the recent report of 2008’s number of church membership, this means that the current Mormon population will not double until 2043. By then, we’ll be 27 million strong. To put this in perspective, that’s about the number of today’s Seventh-day Adventists, or the Pentecostal World Fellowship (International Bulletin of Missionary Research, vol. 31, no. 1, p. 30). Or, that’s still less than the number of Baptists in the U.S. or Methodists, Lutherans, and Presbyterians of the U.S. combined in 2001.

Working off this chart, I expect to identify factors that contributed to sustained growth for the church and periods of decline. Certainly worth noting how Latter-day Saints have kept themselves above linear growth, but find themselves also struggling to keep pace with previous periods of expansion.