Codes for the BMI variable


#1

Below are the codes for the Body Mass Index (BMI) variable (not the bmicalc) on IPUMS .

0000: NIU

9980: 99.8+
9999: Unknown

I thought that those with the BMI of 99.8 and over were coded as 9980.

However, when I tabulate the BMI variable (across several years before and 10 years after 1997), I found that 83 people for 99.90 and 2,586 people for 99.99 and there were no observations for 9980 and 9999. Are there different codes for the variable?

Please see the tabulated results below.

Thanks for your answer in advance!

Variable | Obs Mean Std. Dev. Min Max

-------------±--------------------------------------------------------

bmi | 156,878 13.61521 17.91787 0 99.99

. tab bmi if bmi ==99.99

no observations

. tab bmi if bmi ==99.90

no observations

. tab bmi if bmi >99.8

Body mass |

index | Freq. Percent Cum.

------------±----------------------------------

99.90 | 83 3.11 3.11

99.99 | 2,586 96.89 100.00

------------±----------------------------------

Total | 2,669 100.00


#2

The BMI variable is stored as a four digit number with two implied decimals (as stated in the BMI codes tab). This means that when you download the data in a fixed-width format the BMI values range from 0001 to 9999. When the data is then read into a stats package, such as Stata or SPSS, the syntax file provided by IPUMS includes code to divide in the implied decimals so the range of values for BMI becomes 00.01 to 99.99

The 99.90 values you are seeing are all from the 1992 sample and should be treated as 99.99 (NIU). The IPUMS Health Surveys team is aware of the issue and it will be corrected with the next data release.

I hope this helps. I will let the IPUMS Health Surveys team know that this was not clear and hopefully we can develop a more clear description.