Writing in 1927, French observer Andre Siegfried described Protestantism as America’s “only national religion.” To miss this, Siegfried advised, is “to view the country from a false angle.” Now, less than a century later, a major research report provides proof that Protestantism no longer represents a clear majority of Americans.

Researchers Tom W. Smith and Seokho Kim of the National Opinion Research Center [NORC] at the University of Chicago have released “The Vanishing Protestant Majority,” a report documenting the declining membership of Protestant churches in the nation.

The decline of American Protestantism will come as a shock to many observers, whose understanding of American religion was well summarized by sociologist Will Herberg in his classic 1955 study, Protestant-Catholic-Jew. Herberg characterized America at the midpoint of the twentieth century as a population settled into a tripartite religious identification made up of three great “denominations”–Protestantism, Catholicism, and Judaism. Celebrating this renegotiation of the American religious establishment, Herberg observed: “In net effect, Protestantism today no longer regards itself either as a religious movement sweeping the continent or as a national church representing the religious life of the people; Protestantism understands itself today primarily as one of the three religious communities in which twentieth century America has come to be divided. The ‘denominational’ system–the word ‘denomination’ here referring both to the religious community and to the denomination in its more restricted sense–has become part of the basic assumptions of Protestants about America, as it has become part of the basic assumptions of all Americans.”

According to the NORC study, Americans identifying themselves as “Protestant” fell from 63 percent to 52 percent between 1993 and 2002–a massive decline in less than one decade. According to the University of Chicago press release, the percentage of Americans identifying themselves as Protestant “has been falling and will likely fall below 50 percent by mid-decade and may be there already.”

The NORC study is based on a sizeable research sample, tested to be representative of the U.S. population. The study is not without methodological difficulties. For one thing, the definition of Protestantism used in the report includes “all post-Reformation Christian faiths.” Defining the issue sociologically rather than theologically, the analysts included members of The Church of Jesus Christ of Latter Day Saints [Mormons] and other non-Christian groups in the Protestant sample. Some New Age devotees were also included under the Protestant classification.

Nevertheless, methodological issues aside, the group’s extensive research is sufficient to prove the validity of its central thesis–that Protestantism is declining relative to the total U.S. population.

The rapid decline of the nation’s Protestant majority is an issue of significant sociological interest–along with the percentage of Americans claiming no religious preference and the rise of non-traditional religions in American culture. The report offers interesting points of analysis, including the fundamental failure of most Protestant denominations to evangelize and assimilate their own youth and young adults, and the fact that the nation’s immigrant groups have not followed the older pattern of eventual identification with the nation’s Protestant majority. Denominations concerned about membership losses and evangelistic opportunity will note both developments with grave concern. Nevertheless, churches needing this report to awaken themselves to trends as obvious as these are probably beyond help already.

The loss of young adults is the trend with the most devastating long-term consequences. Researcher Tom W. Smith told The Chicago Sun-Times: “There is some evidence that a large portion of this problem is that a fair number of marginal Protestants are not really engaged in their faith and therefore didn’t pass it on to their kids. The mom and dad would say, for example, ‘Yeah, we’re Methodists,’ but they never went to church. They’d baptize their kids, and that’s about it.”

That statement goes a long way towards explaining the entire pattern of Protestant decline. Though these researchers were primarily concerned about the sociological factors that produced Protestant losses, the larger and more important issues are essentially theological. Among mainline Protestant denominations, theological liberalism has eroded the entire system of Christian doctrine, leading to the evaporation of faith and the secularization of those churches. Once the churches have been thoroughly secularized, what value remains in church membership and denominational identification?

Theological liberalism became evident in the mainline Protestant denominations by the early 1920s. Historian William R. Hutchison of the Harvard Divinity School has traced the erosion of mainline Protestant denominations throughout the twentieth century. Hutchison notes that the denominations affiliated with the liberal National Council of Churches have all experienced steady decline. Accommodating themselves to the spirit of the age, these churches embrace theological and moral relativism in an effort to remain “relevant” to a pluralistic culture.

Several years ago, sociologists Dean R. Hoge, Benton Johnson, and Donald A. Luidens described the result of this process as “lay liberalism” that constitutes the belief system held by Protestant baby boomers. This “lay liberalism” rejects orthodox Christian doctrines such as belief that faith in Christ is necessary for salvation, and renegotiates Christian moral principles in line with permissive sexuality.

In Vanishing Boundaries: The Religion of Mainline Protestant Baby Boomers, Hoge, Johnson, and Luidens explain that lay liberalism erases clear boundaries separating believers from unbelievers. Without a clear “faith boundary,” identification with Protestantism–and Christianity itself–becomes socially meaningless.

The Vanishing Boundaries study, along with the NORC report, acknowledges the continued growth of conservative Protestant groups, commonly designated as evangelical. These evangelical denominations and churches continue to grow, even as they maintain clear boundaries between belief and unbelief. The existence of these boundaries explains the strong sense of membership and the high rate of participation commonly found in evangelical congregations. As Hoge, Johnson, and Luidens observed: “Our findings show that belief is the single best predictor of church participation, but it is orthodox Christian belief, and not the tenets of lay liberalism, that impels people to be involved in church.”

This is just common sense, of course. But it is precisely the kind of common sense that is commonly ignored or discarded by those who would rather believe otherwise. The churches that are most insistent on being relevant are those most willing to sacrifice biblical truth and the structure of Christian doctrine in order to prove their commitment to cultural expectations. Eventually, these churches become so identified with the culture that all distinctiveness disappears.

The sacrifice of truth for a constantly changing concept of relevance leads necessarily to the relativizing of the Gospel itself, and the undermining of biblical authority. Once these are sacrificed, authentic Christianity is abandoned and all motivation for membership disappears. If beliefs do not matter, the churches themselves do not matter.

The NORC study is wake-up call for Christianity in America. The trend-line is clear: Without a firm grasp of the Gospel, a bold commitment to biblical authority, and a clear vision for evangelism, churches and denominations are destined for decline and eventual dissipation. It shouldn’t take a team of sociologists to teach us something we should already know.