According—appropriately enough—to the book of Numbers, on the first day of the second month of the second year after the exodus from Egypt, God commanded Moses to take a census of the children of Israel (Numbers 1:1-2). Elsewhere in the Old Testament, a systematic count of God’s people was associated with wickedness (e.g., 2 Samuel 24:10); but the Numbers passages suggests that a precise enumeration was a good thing. With the help of 12 scribes, Moses generated a record of every male over the age of 20 and listed them by tribe, clan and family.

In August, Mennonite World Conference issued its triannual census of global Anabaptists. For more than 20 years, MWC has been keeping track of our numbers, thanks largely to the tireless if mostly unheralded efforts of staff member Eleanor Miller, who has written hundreds of emails and patiently sifted through reams of data in an effort to keep up with the shifting kaleidoscope of Anabaptist-Mennonite groups throughout the world.

As always, the results of this year’s census were fascinating.

On the basis of the most recent numbers, the Anabaptist-Mennonite family increased by 62 new groups and 350,000 members during the past three years, for an overall growth in membership of 19.7 percent. In Africa, the increase was a phenomenal 34.8 percent. Yet these figures—broken down by continent, country and group—conceal as much as they reveal.

One significant challenge to the MWC census, for example, is determining exactly which groups qualify for inclusion in the census. Church bodies that are members of MWC are clear enough, but if the survey is to include all “Anabaptist” groups, the boundaries become significantly more blurred.

Brethren in Christ groups have long been included, but what about the Church of the Brethren? The Hutterites are in, but what about the Bruderhof? The Old Order Amish and Old Colony Mennonites did not ask to participate but are included nonetheless; but what about the Missionary Church or the Apostolic Church, both of whom have historical connections to the Anabaptist tradition but have consciously distanced themselves from that identity? Or what about the growing number of active participants in Anabaptist Networks, who often retain formal membership in their own denomination?

One reason for the remarkable growth over the past three years was the decision to include—for the first time, and at its request—the Church of the Brethren. So, like baseball statistics in a post-steroid era, MWC figures going forward will need to include an asterisk for the year 2015, noting that this anomaly accounts for a significant portion of our increase in numbers.

But the larger question remains: What are the appropriate qualifications for inclusion in the census?

Another challenge MWC staffers face is sorting through the various criteria groups use to determine membership. Not all churches distinguish clearly between members and attenders; not all groups link membership to baptism. Some groups tally only baptisms and deaths, not accounting for members who move into other denominations. Some groups clearly inflate their numbers, sometimes to absurd proportions, while other groups are wary about passing on any figures.

Lurking behind all of this numerical hand-wringing is an even bigger question: Why do these figures matter at all? Part of our fascination with these numbers may be a secret desire to be relevant.

In a market-driven culture, numerical growth is often a self-evident measure of success. “If you are not growing,” consultants warn, “then you must be dying.”

More positively, the numbers invite us to celebrate those parts of our body that are heeding Christ’s call to “make disciples in all nations.” Measuring changes in membership over time, be it growth or decline, can also be instructive, helping illuminate areas of strength or weakness. I think it useful, for example, to note that the membership of Mennonite Church USA now constitutes slightly less than 5 percent of the global Anabaptist family. As we struggle to assert the right definitions of Christian faithfulness here at home, we should remind ourselves that the overwhelming majority of Anabaptists in the world do not look like us.

In the end, I’m deeply grateful to Eleanor Miller and the staff at MWC for keeping track of our numbers.

I love the MWC world membership map, with its colored dots showing our proportions around the world, and I praise God that we are growing as a church body. But we should also read these statistics cautiously, recognizing the limitations of the data, recalling that the path of discipleship is narrow, and that membership numbers, important though they may be, are not the only measure of spiritual health and vitality.

John D. Roth is professor of history at Goshen (Ind.) College, director of the Institute for the Study of Global Anabaptism and editor of Mennonite Quarterly Review.