How Many People Are Named William Ildefonso?
There are approximately 5 people named William Ildefonso living in the United States today. That makes this name combination very rare, occurring at a rate of about 1 in 68,550,868 Americans.
This estimate combines SSA birth records for the first name William with Census Bureau frequency data for the surname Ildefonso. Below you will find a breakdown of both names, including popularity trends, gender data, and ancestry information.
Estimated People with This Name
5
1 in 68,550,868 Americans
Combination Rarity
Very Rare
First Name
View full profileWilliam
Last Name
View full profileIldefonso
William: Popularity Over Time
Year-by-year SSA birth registrations for the first name William. The peak year was 1947 with 67,155 births. The average person named William today is 54 years old.
Ancestry of the Ildefonso Surname
Self-reported race and ethnicity breakdown for people with the surname Ildefonso, from the 2010 U.S. Census Bureau.
How we calculated this
The first name "William" has an estimated frequency of 0.681% among living Americans, based on SSA birth records from 1880 to 2024 adjusted for mortality using CDC 2023 life tables.
The surname "Ildefonso" appears at a rate of 0.21 per 100,000 people in the 2010 U.S. Census.
Multiplying these frequencies against the U.S. population of ~343 million gives 5 estimated people. This assumes first names and last names are statistically independent. Full methodology.
Other people named William
Other people with the surname Ildefonso
William Ildefonso: Questions and Answers
How many people are named William Ildefonso?
We estimate approximately 5 people named William Ildefonso are alive in the United States today. The first name William is shared by 2,335,115 Americans, and the surname Ildefonso is shared by 705.
How rare is the name William Ildefonso?
This name combination is classified as Very Rare, occurring at a rate of about 1 in 68,550,868 Americans. The first name William is very common and the surname Ildefonso is very rare.
Is William a male or female name?
William is predominantly male, with 99.6% of bearers being male and 0.4% female. It peaked in popularity in 1947 and the average bearer today is 54 years old.
Where does this data come from?
First name data comes from the Social Security Administration (1880 to 2024), adjusted for survival using CDC 2023 life tables. Surname data comes from the 2010 U.S. Census Bureau. Full methodology.
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