The Bootcamp for GeneaBloggers blog has a great link to a site called PublicProfiler/worldnames. You can enter a surname and find its origin and prevalence.
With every database, web site, or anything searchable in regard to genealogy, I always use Lenertz as my test surname. There aren't many Lenertz's to begin with and I know where they are. The results I get for Lenertz genealogy in any given search aid tell me how good the product is. I have to say, this time the end result was pretty close.
Here's what I learned:
Luxembourg is a Lenertz hub. There are 93.52 people named Lenertz or every million people there.
There are 1.88 people per million named Lenertz in the United States.
Minot, North Dakota and Mankato, Minnesota are the top U.S. cities for the name Lenertz. My Lenertz line hailed from Mankato, and originally came from Luxembourg. I knew there was a Lenertz pocket in North Dakota, but didn't realize it was so big. Also, I'm surprised Iowa didn't make the list.
Guess that settles that. Lenertz people are truly one in a million.