"The remarkable growth is almost entirely due to the Amish birth rate - many Amish families have five or more children. Kraybill said the Amish retain about 85 percent of the young adults who have to decide whether to remain in the church. The Amish marry within the community, and the total number of converts nationwide is believed to be less than 100, he said.Another important point in the AP article: "Nearly all Amish descended from a group of about 5,000 in the early 20th century." The title of the article might make one think this "boom" is something new and perhaps short-lived (like the post-WWII baby boom). Instead, this is simply evidence of what the ongoing procreative divine ordinance of God achieves when left relatively unhindered, showing us the rate at which the rest of Christendom would have grown since the "early 20th century" if it hadn't adopted the Margaret Sanger doctrine of Planned Parenthood. (N.B.: even the Amish community has not been entirely unaffected by this. Note the second paragraph down on this page.)
"About half the Amish are under 18 years old, meaning the community tends to focus much of its energy on young people and schools, Kraybill said."
The AP story points out that the "total number of [Amish] converts nationwide is believed to be less than 100."
By contrast, it seems Lutherans are now almost entirely dependent upon conversion to maintain their numbers, and we all know the minimal teaching (if any) that passes for "conversion" in most "Lutheran" churches. Here is a recent anonymous comment on L&P that is worth considering. It quotes this earlier post by Pastor Curtis.
HT: Rebekah at CSPP