Maybe it has been shown, but not in the post I was responding to, which covered the 20th century, not the 19th century.
I don’t know what the numbers are for the 19th century, but I can think of reasons the 20th century American numbers would be different than the 19th century numbers.
It has been shown/documented that the the LDS propagated myth of 19th century marriages being in the teenage years is false.