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Surveillance Research Program

How to Compute Age-Adjusted Rates in Joinpoint

For a detailed explanation on how to calculate age-adjusted rates, please refer to the following web site:

http://seer.cancer.gov/seerstat/tutorials/aarates/step1.html

For Joinpoint to compute age-adjusted rates, each input data record must have the following variables IN THIS ORDER:

  1. All cohort-defining variables
  2. Independent variable
  3. Adjustment variable (this is typically an age variable)
  4. Count
  5. Population
  6. Standard Population


The following requirements will be applied to each cohort when age-adjusted rates are computed by Joinpoint:

  • The data has to be sorted using the following variable order:
    • All cohort defining variables
    • Independent variable
    • Adjustment variable
  • Count values must be greater than or equal to zero.
  • Population values must be greater than or equal to zero
  • If the population value is zero, the associated count must also be zero.
  • The count must not be greater than the associated population.
  • Standard Populations values must be greater than zero.
  • The Adjustment Variable must have the same categories (in the same order) for each By Variable/Independent Variable combination.


Below is an example of an input data file correctly structured for Joinpoint to compute age-adjusted rates.The data file contains one by variable (sex:1 = Male, 2 = Female) and the independent variable is Year (values are 1980 thru 2000 inclusive).For each Sex/Year combination, there is a complete set of adjustment variable values (00 years to 85+ years). Please note that the standard population appears on every data record and the value corresponds to the associated age group.

By Variable (Sex) Independent Variable  (Year) Adjustment Variable (Age) Count Population US 2000 Standard Populations
1 1980 00 years 29 139,879 3,794,901
1 1980 01-04 years 87 553,189 15,191,619
1 1980 05-09 years 67 736,212 19,919,840
1 1980 10-14 years 71 770,999 20,056,779
1 1980 15-19 years 87 651,309 19,819,518
1 1980 20-24 years 177 639,159 18,257,225
1 1980 25-29 years 290 676,354 17,722,067
1 1980 30-34 years 657 736,557 19,511,370
1 1980 35-39 years 1,072 724,826 22,179,956
1 1980 40-44 years 1,691 700,200 22,479,229
1 1980 45-49 years 2,428 617,437 19,805,793
1 1980 50-54 years 2,931 516,541 17,224,359
1 1980 55-59 years 2,881 361,170 13,307,234
1 1980 60-64 years 2,817 259,440 10,654,272
1 1980 65-69 years 2,817 206,204 9,409,940
1 1980 70-74 years 2,744 172,087 8,725,574
1 1980 75-79 years 2,634 142,958 7,414,559
1 1980 80-84 years 1,884 99,654 4,900,234
1 1980 85+ years 1,701 92,692 4,259,173
1 1981 00 years 34 141,456 3,794,901
1 1981 01-04 years 97 562,059 15,191,619
1 1981 05-09 years 72 738,302 19,919,840
... ... ... ... ... ...
1 2000 80-84 years 2,176 100,249 4,900,234
1 2000 85+ years 2,001 94,875 4,259,173
1 2000 80-84 years 2,176 100,249 4,900,234
2 1980 00 years 37 159,829 3,794,901
2 1980 01-04 years 101 562,001 15,191,619
... ... ... ... ... ...
2 2000 85+ years 2,521 96,228 4,259,173

Below is an example of how an age-adjusted rate is computed. The age-adjusted rate is 400.3 and is the sum of the interim values over all age groups.  The interim value in each row is equal to (Crude Rate * Age Distribution of Std Pop).

Age Count Population Crude Rate US Standard Populations Age Distribution of Std Pop Interim Value
00 years 29 139,879 20.7 3,794,901 0.013818 0.29
01-04 years 87 553,189 15.7 15,191,619 0.055316 0.87
05-09 years 67 736,212 9.1 19,919,840 0.072532 0.66
10-14 years 71 770,999 9.2 20,056,779 0.073031 0.67
15-19 years 87 651,309 13.4 19,819,518 0.072167 0.96
20-24 years 177 639,159 27.7 18,257,225 0.066478 1.84
25-29 years 290 676,354 42.9 17,722,067 0.064530 2.77
30-34 years 657 736,557 89.2 19,511,370 0.071045 6.34
35-39 years 1,072 724,826 147.9 22,179,956 0.080762 11.94
40-44 years 1,691 700,200 241.5 22,479,229 0.081852 19.77
45-49 years 2,428 617,437 393.2 19,805,793 0.072117 28.36
50-54 years 2,931 516,541 567.4 17,224,359 0.062718 35.59
55-59 years 2,881 361,170 797.7 13,307,234 0.048454 38.65
60-64 years 2,817 259,440 1,083.8 10,654,272 0.038794 42.12
65-69 years 2,817 206,204 1,366.1 9,409,940 0.034264 46.81
70-74 years 2,744 172,087 1,594.5 8,725,574 0.031772 50.66
75-79 years 2,634 142,958 1,842.5 7,414,559 0.026998 49.74
80-84 years 1,884 99,654 1,890.5 4,900,234 0.017843 33.73
85+ years 1,701 92,692 1,839.4 4,259,173 0.015509 28.53
All Ages       274,633,642 1.000000 400.3