In her book Total Truth, Nancy Pearcey writes that churches that change are churches that decline.

Well before the American Revolution, leading scholars at Harvard and Yale had become Unitarian. Instead of exhorting their congregations to repent and be saved, they delivered elegant styled lectures on "reasonable religion," with the supernatural elements increasingly stripped away. When the First and Second Great Awakenings broke out, the liberal clergy firmly opposed them, declaring themselves on the side of "Reason" against the revivalists’ "religion of the heart."

That was a sure recipe for failure. It is a common assumption that, in order to survive, churches must accommodate to the age. But in fact, the opposite is true: In every historical period, the religious groups that grow most rapidly are those that set believers at odds with the surrounding culture. As a general principle, the higher a group’s tension with mainstream society, the higher its growth rate.

In 1776, the three largest Christian denominations in the United States were Congregationalists (20.4% of all religious adherents), Episcopalian (15.7%) and Presbyterian (19.0%). Those were the established churches that sought to separate "Reason" from faith, and thus conform to the current culture. By 1850 they had all dropped radically and in direct proportion to their abandonment of traditional Christian theology: Congregationalists (4.0%), Episcopalians (3.5%) and Presbyterian (11.6%).

They were overtaken by the Baptist (16.9 to 20.5%) and the Methodists (2.5% to 34.2%) who grew because of evangelistic fervor and who preached a gospel that "cost" something. Followers had to be "in, but not of the world."

Today the Congregationalists have all but ceased to exist (0.7%). Episcopalian are down to only 1.7% of the US population. Presbyterians are at 2.7% (and they have the largest percentage of conservative, evangelical churches and members). Baptists have over taken Methodists as the largest Protestant denomination, as the Methodists have drifted toward a more liberal theology. Baptists represent 16.3% of the US population, while Methodists are at 6.8%.

Churches that are growing the most are often non-denominational (up to 1.2% of US population in 2002) and Pentecostal churches (up to 2.8%) both of whom are largely conservative in their theology and evangelical in their practices.

These numbers have only been in the United States, but the worldwide numbers are even more telling. At the current rate of growth, in a few decades China will be over 30% Christian. In nations where the government and culture is opposed to Christianity, the Church is flourishing and adding members on a daily basis.

While the case is continually made that churches which hold on to "ancient" teachings are more likely to die out, the numbers indicate that churches who seek to adopt the current line of secular thinking are the ones who lose membership.

One explanation may be that churches who seek to adapt cannot offer followers a sense of consistency. Denominations that are led by cultural dictates cannot give adherents a solid foundation as their theology changes to suit outside influences.

Whatever the case, the data support the fact that a church which keeps its doctrine consistent and its theology conservative will experience growth, while churches that view doctrinally change as necessary to cultural relevance will experience a decline in membership and relevance.