There are times when I really feel the pain of the brilliant folks who work with the polling and research division of the Pew Forum on Religion & Public Life. After all, how would you like to try to put the astonishingly complex world of American religion into those short, punchy phrases that pollsters have to use? You have to use words that mean something to people on sidewalks and in living rooms, yet the phrases also have to have some connection to the actual doctrines and historical facts that are used by insiders and scholars.

Then, to make matters worse, all of this is going to be reporting in mainstream public media in short, short and shorter reports, at times by reporters who have no clue what they are doing.

You can see the problems, even when Pew Forum research ends up in the hands of veteran, skilled reporters who definitely know what they are doing. Here is Jacqueline L. Salmon of the Washington Post, describing the new Pew Forum report that attempts to shed light on the reasons that Americans give for switching from one religion to another.

More Americans have given up their faith or changed religions because of a gradual spiritual drift than switched because of a disillusionment over their churches' policies, according to a new study released today which illustrates how personal spiritual attitudes are taking precedence over denominational traditions.

The survey by the Pew Forum on Religion & Public Life is the first large-scale study of the reasons behind Americans switching their religious faith and found that more than half of people have done so at least once during their lifetime. Almost three-quarters of Catholics and Protestants who are now unaffiliated with a religion said they had "just gradually drifted away" from their faith. And more than three-quarters of Catholics and half of Protestants currently not associated with a faith said that, over time, they stopped believing in their religion's teachings.

The problem, of course, is that it is almost impossible to precisely define what it means to "change religions." Is there, for example, a difference between "changing" and "converting"?

Clearly, if people convert from Christianity to Judaism, they have changed religions. But most of the numbers, in this poll, reflect changes inside Christianity, including the hip change from membership in a specific church to the freelance "spiritual, not religious," but still "Christian sort-of" status. The pollsters knew this and included a crucial line in their survey: "Raised Protestant, now different Protestant faith."

So if you are Southern Baptist and become an Episcopalian, that is a change.

However, truth be told, I have known people whose faith changed more -- in terms of doctrinal content -- when they went from membership in a Southern Baptist church to being part of a "moderate" Southern Baptist church, than if that those same people had gone from membership in Southern Baptist congregations to membership in a low-church, evangelical Anglican parishes.

How about Southern Baptist to American Baptist? Episcopalian to Charismatic Episcopalian? A cultural Greek Orthodox parish to a convert-friendly Greek Orthodox parish? Evangelical Lutheran and Missouri-Synod Lutheran? Reform Jew to Orthodox Jew? Etc., etc.

Like I said, I feel the Pew folks' pain. The online talking points about this study hint at another problem that is out there:

Catholicism has suffered the greatest net loss in the process of religious change. Many people who leave the Catholic Church do so for religious reasons; two-thirds of former Catholics who have become unaffiliated say they left the Catholic faith because they stopped believing in its teachings, as do half of former Catholics who are now Protestant. Fewer than three-in-ten former Catholics, however, say the clergy sexual abuse scandal factored into their decision to leave Catholicism.

In contrast with other groups, those who switch from one Protestant denominational family to another (e.g., were raised Baptist and are now Methodist) tend to be more likely to do so in response to changed circumstances in their lives. Nearly four-in-ten people who have changed religious affiliation within Protestantism say they left their childhood faith, in part, because they relocated to a new community, and nearly as many say they left their former faith because they married someone from a different religious background.

How much of this, in other words, is simply generic church shopping? The marriage factor is also huge for people whose faith is not that central to their lives. It's easy for people to switch when the switch doesn't mean that much to them.

Over at USA Today, Godbeat veteran Cathy Lynn Grossman's report also included a sobering summary for Catholic leaders. It appears that the mainline Protestant-ization of American Catholicism continues at a rapid pace. Perhaps generic, everyday Catholicism isn't all that radically different these days?

Catholicism has suffered the greatest net loss in the process of religious change: The 10% of U.S. adults who have quit the church vastly outnumber the 2.6% who are incoming Catholics. Two in three who became unaffiliated -- and half of those who became Protestant -- say they left the Catholic Church because they "stopped believing its teachings." The sexual abuse scandal was a factor for fewer than three in 10 former Catholics.

In conclusion, let me note one other issue that may be hidden down in this Pew Forum research (and I intend to ask about it).

Anyone who works in the wider world of modern religion knows about the so-called 80-20 rule. This states that about 80 percent of the work, worship and giving is done by about 20 percent of the membership, the most dedicated members who have the strongest ties to their particular faith and to the content of its doctrine.

What happens when these people convert from one faith to another? What are the doctrinal fuses that must be lit to drive a devout believer -- say a clergyperson -- from Canterbury to Rome, from Nashville to Geneva, from Jerusalem to Athens? I know, from experience (my Orthodox parish is about 90 percent converts), that this is a radically matter than making a church switch due to marriage or a change in zip code.

Alas, how do you put that kind of human blood, sweat and tears into a poll questionnaire?