Genealogy: Using the census to calculate the birth year of your ancestor

Census BirthBy Barry J. Ewell
As you track your ancestor through the U.S. Federal Population Censuses, I have often used the age to help  me

  • Identify individual members of the family
  • Provide clues to confirm I have the right person/family unit as you search each census
  • Provide clues as to relationship in the family
  • Provide clues if I have the right female when surnames change through marriage
  • Provide clues when people use nicknames and other name variations from one census to the next

When you are working with age in the census, you still have to be careful.   Age/birth year provided on the census is not primary source like a birth certificate or church record.  It is one individual telling you the ages of the household.   If I were to answer the census question today on the age of my family I would be close but not exact.  I would start with how old my oldest daughter is and then subtract two years for each child.  Now if you were to ask my wife the same question, she would have no problem giving you the age of every member of our family right down to the month. My point is simple, information provided the census taker varies from household to household and it’s also about the quality of the census taker hearing and writing down what they heard correctly.

I have found it important to use the census age information to calculate range of possible birth dates and years of the people listed the family unit I am researching. I have prepared a birth year reference chart for each census to help you identify an estimated birth year for each ancestor.  See below for links to various census charts.

But you can manually do it also.  Let’s say the Census Taker dropped by the John Stewart home in June 1910.  On that date John was 69 years old.  Simply subtract the age of the person from the census year.  The subtraction problem would be 1920-68=John was born in about 1851.  Notice I said that John was born about 1851. From the time each census begins and ends, there is a lag time, birth dates of individuals, competency of the person giving the answers to know the birth age so forth which I don’t have I am not accounting for in my calculation.  This means I am going to say that John could have been born based on 1920 census between the years of 1850 and 1852 with 1851 being the target year.  As I research other census, I was able to conclude that 1851 was the most likely year of his birth.

How truthful were people about their age?  I have research 1,000’s of family members though the census years and found them to be 99.8 percent truthful providing the same ages variances from one census to the next. The following example is provided to show how the age was used to help identify the John Isaac Stewart through 1930-1860 U.S. Federal Population Censuses.
Census Age

  • 1860 John is age 10 and the fifth son of James M. and Susanah Stewart.
  • 1870 John is age 19.  His older brothers Daniel, Archibald, and Amos have left home.  Three sisters are added Frances, Jane, and Bell.
  • 1880 John is age 29. He has married Nolie and they have a son Guy, age 2.
  • 1890 Census destroyed.

Census Age

  • 1900 John is age 49. Nolie is now referred to as Penola is age 58. Children at home are the sons Frank 19, Blanchard 16, Percy 13, Clarence 11, and Thomas 3.  Guy has not age 22 has left home. Age was important to confirm I had the right family.  Nollie was the nickname of Panola could have been either a new wife or same person. The age of Nolie and Panola were the same so I was able to use that as a clue to make sure I was working with the right group of people.
  • 1910 John is age 59 and Penola is 58. Sons that are home are Blanchard 26, Percy 23, Clarence 20, Harold 20, Thomas is now referred to as Jay 13
  • 1920 John is age 69 and Panola is 68.  Son that are home are Blanchard 35, Robert 33 Clarence 30, and Jay 23.
  • 1930 John has died and Panola 78 is the only member of the household.

U.S. Federal Census birth year reference charts
Click on any of the following years and you will be take that years’ census birth reference chart:

U.S. Federal Census Tutorials
Click on any of the following years and you will be take that years’ census tutorial:

  • 1790, 1800, 1810, 1820, 1830, 1840, 1850, 1860, 1870, 1880, 1890, 1900, 1910, 1920, 1930, 1940