[Facts] Re: Middle names and statistics
My understanding is that statistics are not officially collected for middle names. The U.S. Social Security Administration publishes data about first-name usage only.
In addition, the SSA data does not allow non-alphabetic characters or spaces in a first name, nor capital letters apart from the first letter.
So, if parents give their child a first name such as Mary-Ann, it will be recorded as Maryann, with the hyphen and capital A removed.
If they name her Mary (first name) Ann (middle name), even though they intend to call her by the double name Mary Ann, it will be recorded as Mary.