Hello, apologies if this is a silly question. I am looking to generate population estimates of birthplace (bpld) by year of immigration (yrimmig) (2011-2024) for a select group of countries using the IPUMS online analysis system. I originally used the ACS 2001-2024 option as I figured it would be better to include as much data as possible across those years of interest. However, the results I get for the weighted N are definitely wrong (in some cases many, many times more than we would expect based on DHS data).
When I run the exact same cross tab with the ACS 2019-2023 5-year, the results are much more reasonable, in many cases undercounting what DHS shows.
I would still prefer to use as many years as possible as I will next be using the micro data for subsequent analyses. I did notice that the instructions say “Considerations when using the multi-year data samples: Analyses should include the “year” variable.”. How would I include year in this case? I tried to filter by the years of interest and the results are still unreasonable. Does anyone have any other suggestions? Very grateful for the support!
Each 1-year American Community Survey (ACS) sample is designed to provide estimates for a single year. For example, the 2024 ACS is collected during the 2024 calendar year and is designed to provide estimates for 2024. The ACS 2001-2024 option combines all of the years from this range into a single sample, meaning that analyses using this option provide a single estimate for the entire 24 year period (unless the variable YEAR is used). For example, if a group has a population size of 100,000 in 2001, and this number stays constant through 2024, then the estimate for the population size using the ACS 2001-2024 option would be 2.4 million (100k * 24). Note that pooling multiple 1-year samples is only an issue for estimates of frequencies or counts but not for other estimates like means or ratios. There are a number of different approaches that you could use to adjust these estimates:
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You can obtain an average estimate for the 2001-2024 period by dividing the estimate by the number of samples. In the above example, this would mean dividing 2.4 million by 24 (since this period includes 24 total years of data) to obtain an estimate of 100k. This will give you the average population size of the group across all 24 years.
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You can obtain estimates for each individual year or for a smaller group of years by adding “year” into the Selection Filter(s) field. For example, you can add year(2011-2024) to obtain estimates for this 14 year period. You will still need to divide weighted N’s by the total number of sample years.
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You can use the 5-year ACS sample, which is designed to produce estimates that are representative over the five-year period. For example, the ACS 2019-2023 5-year sample will produce estimates for the 2019-2023 period as a whole. These do not need to be divided by the number of years since this is a single sample.
For each of these approaches, you should be aware that year of immigration (YRIMMIG) will be correlated with the years that you include in your analysis. For example, for an estimate the number of people who immigrated to the U.S. in 2015 using data from 2001-2024, most of the ACS samples will have zero people meeting those criteria. Getting an average over a period that includes samples from years prior to the YRIMMIG codes that you are interested in may not be very helpful.
Finally, please note that the ACS is a survey that is self-administered by 1% of US households each year. Estimates from the ACS will not perfectly replicate estimates from other sources or data from administrative records.