Thaddeus Osullivan
There are approximately 1 people named Thaddeus Osullivan living in the United States today. That makes this name combination very rare, occurring at a rate of about 1 in 342,754,338 Americans.
This estimate combines SSA birth records for the first name Thaddeus with Census Bureau frequency data for the surname Osullivan. Below you will find a breakdown of both names, including popularity trends, gender data, and Census demographics where available.
Expected bearers
1
1 in 342,754,338
Named Thaddeus
18K
Alive today
Named Osullivan
14K
Alive today
US population
343M
Denominator
Estimated living: 18K
Rarity: Uncommon
Gender: Male
Peak year: 2016
Average age: 39
Top Census group: White (61.2%)
Estimated bearers: 14K
Rarity: Uncommon
Census rank: #2,941
Per 100K: 4.01
Top ancestry: White (91.1%)
First name trend
Thaddeus: popularity over time
Year-by-year SSA birth registrations for the first name Thaddeus. The peak year was 2016 with 416 births. The average person named Thaddeus today is 39 years old.
Babies born per year
Demographics
Ancestry and ethnicity for Thaddeus
Self-reported race and ethnicity breakdown for people with the first name Thaddeus, from the 2020 US Census Bureau first-name tables. The largest published group is White at 61.2%.
The bar chart below shows how people with the first name Thaddeus described their own race and ethnicity on the 2020 Census form. These are self-reported numbers, and they describe the population who happened to carry the name Thaddeus at the time of the Census. A first name does not determine a person's race or ethnicity.
- White61.2% · 9,488
- Black or African American27.3% · 4,230
- Hispanic or Latino4.7% · 723
- Two or more races4.6% · 714
- Asian and Pacific Islander1.5% · 239
- American Indian and Alaska Native0.7% · 111
Ethnicity
Ancestry of the Osullivan surname
Self-reported race and ethnicity breakdown for people with the surname Osullivan, from the 2020 US Census Bureau. The largest group is White at 91.1%.
The bar chart below shows how people with the surname Osullivan described their own race and ethnicity on the 2020 Census form. These are self-reported numbers, and they describe the population who happened to carry the surname Osullivan at the time of the Census. A surname does not determine a person's race or ethnicity.
- White91.1% · 10,903
- Hispanic or Latino3.4% · 409
- Two or more races2.8% · 340
- Black or African American1.7% · 201
- Asian and Pacific Islander0.9% · 107
- American Indian and Alaska Native0.1% · 11
Methodology
How we calculated this
The first name Thaddeus has a living-bearer frequency of 0.0054% of the US population, based on 18,360 estimated living Americans carrying this first name (from SSA birth records going back to 1880, adjusted for mortality using CDC life tables).
Even though the Census Bureau now publishes first-name tables, we do not use that file as the main first-name input for this estimate. The latest first-name Census snapshot is from 2020, which makes it 6 years old today. Because Census first-name data is only released once every 10 years, SSA birth records plus CDC survival rates give a better current estimate of how many people are likely alive with the name Thaddeus right now.
The surname Osullivan appears at a rate of 4.01 per 100,000 residents in the 2020 Census Bureau surname file, which translates to a frequency of 0.0040%.
Multiplying these two independent frequencies against the current US population of 342,754,338 gives an expected count of approximately 1 people with the full name Thaddeus Osullivan. This assumes statistical independence between first and last names, which is a simplification but produces reasonable estimates for most combinations.
Related
Other people named Thaddeus
Related
Other people with the surname Osullivan
FAQ
Thaddeus Osullivan: questions and answers
How many people are named Thaddeus Osullivan?
We estimate approximately 1 people in the United States share the full name Thaddeus Osullivan. That works out to about 1 in 342,754,338 Americans. This is calculated by combining the first-name frequency (0.0054%) with the surname frequency (4.01 per 100K) against the current US population.
How rare is the name Thaddeus Osullivan?
We classify Thaddeus Osullivan as "Very Rare". About 1 in 342,754,338 Americans share this exact first and last name combination.
Is Thaddeus a male or female name?
Thaddeus is predominantly male. Out of 25,771 total SSA registrations, 99.9% were male and 0.1% were female. See the full Thaddeus profile for detailed gender data.
Where does this data come from?
First-name data comes from the Social Security Administration's national baby name files (1880 to 2024). Surname data comes from the 2020 US Census Bureau decennial surname tables. Living-bearer estimates use CDC actuarial life tables to adjust for mortality. Read the full methodology.
How many people are called Thaddeus Osullivan?
For a faster, more casual read, check HowManyOfMe.org — our sister site built around that single question.