The 2025 ACS Data Users Conference will be held on May 29, 2025 (virtual day) and June 3, 2025 (in-person in DC)
Details
  • Views 3536 views
  • Replies 5 replies
  • Subscribers 542 subscribers
  • Users 0 members are here
Labels
Related Census Bureau Resources
Related Forum Threads

1 vs 5 year estimates regarding annual difference in median income

Martha Burke
over 5 years ago

We are trying to calculate the difference in median annual income at the county level between those who are high school graduates vs. those who are less than high school graduates.  There are both 1 year and 5 year estimates from the ACS available.  The goal is to provide a yearly estimate of the difference in income between the two groups (e.g., “in 2013, the annual difference in median income between high school graduates and those with less than a high school education was $X”).  With 1 Year estimates, we could make a statement like that.  With 5 year estimates, the statement would have to be more like, “in 2013-2017, the annual difference in median income between high school graduates and those with less than a high school education was $X”.

 

Understanding that the 5 year estimates are more reliable because the samples are larger and also have smaller margins of error, what would be the better source to calculate the difference by year (i.e., 2013, 2014)?  The 1 year estimates are exactly that, even though the margins of error are larger.  The 5 year estimates share overlapping years, so they are not a true indicator of the difference in a single year.  Since we are looking at county level data, the 1 year estimates include a large sample size, but in comparing the 1 Year and 5 Year data, the actual median values are not wildly different, but the margins of error are very different.  Even though we would ideally like to make a statement about differences by year, would it be better to use the 5 year estimates since they are more reliable? 

Parents
  • over 5 years ago
    Hi Martha,

    It is all in how you want to show the data, if you do indeed need annual, then you should use the 1-year estimates. If you're using the 5-year estimates, then you would need compare every 5 years (i.e. 2013-2017 with 2008-2012).

    keep in mind that ACS estimates are PERIOD estimates. they are estimates derived from surveys collected throughout the survey period. In other words, 2017 1-year data are based on surveys collected throughout all of 2017 and the 2017 5-year estimates are based on surveys collected throughout all 5 years, 2013-2017.

    So a more accurate statement, if using 5-year data, would be something like "For the period 2013-2017, the difference from the prior period (2008-12) in median income between high school graduates and those with less than a high school education was $xx." Maybe someone else can word that better, as it is a long sentence!

    Although, to be honest, in my office we generally refer to the reference year for the 5-year estimates, so we would probably instead say something like "From 2012 to 2017 the different in median income between high school graduates and those with less than a high school education was $x." Then I'd footnote in the sources to explain that "2012" and "2017" refer to data from the 5-year ACS period estimates.

    I would be interested to see how others respond.
Reply
  • over 5 years ago
    Hi Martha,

    It is all in how you want to show the data, if you do indeed need annual, then you should use the 1-year estimates. If you're using the 5-year estimates, then you would need compare every 5 years (i.e. 2013-2017 with 2008-2012).

    keep in mind that ACS estimates are PERIOD estimates. they are estimates derived from surveys collected throughout the survey period. In other words, 2017 1-year data are based on surveys collected throughout all of 2017 and the 2017 5-year estimates are based on surveys collected throughout all 5 years, 2013-2017.

    So a more accurate statement, if using 5-year data, would be something like "For the period 2013-2017, the difference from the prior period (2008-12) in median income between high school graduates and those with less than a high school education was $xx." Maybe someone else can word that better, as it is a long sentence!

    Although, to be honest, in my office we generally refer to the reference year for the 5-year estimates, so we would probably instead say something like "From 2012 to 2017 the different in median income between high school graduates and those with less than a high school education was $x." Then I'd footnote in the sources to explain that "2012" and "2017" refer to data from the 5-year ACS period estimates.

    I would be interested to see how others respond.
Children
  • over 5 years ago in reply to JamiRae
    A factor to consider here is the county population size. If you are talking about New York County, NY (ie Manhattan) then certainly use the 1 year estimates. If you counties include ones with a population of under 250,000 I'd stick with the 5 year estimates. Even in a city of 100,000, where I work, the 1 year estimates can be quite unstable from year to year. The more uneven your data the more time you will need to spend explaining and defending that unevenness.

    It seems to me what is most interesting here is how the trend changes over time - what size is the gap, does it get bigger, smaller, in absolute or percentage terms, etc. Comparing 5 year data will allow you to answer those types of questions.

    This is where I miss the 3 year ACS estimates that were discontinued several years ago. For my purposes, they were a good trade off between currency of information and size of margin of error.
For more information about the American Community Survey Census Bureau Website