Should I compare data year-over-year?
Comparing Data Year-over-Year
We and the US Census Bureau recommend against comparing data across the Census’ American Community Survey 5 year datasets (2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 and 2019) with overlapping years.
The US Census Bureau collects surveys for 5 years and then sums up the responses to produce current year estimates.
- For the 2019 dataset, surveys were collected in 2019, 2018, 2017, 2016 and 2015. Then, the later year survey responses were projected forward (e.g. 2015 income was projected into 2019 dollars).
- The 2018 dataset is made up of surveys that were collected in 2018, 2017, 2016, 2015 and 2014.
There are 4 years of overlapping survey results between the 2019 dataset and the 2018 dataset. If you are doing historical comparison work, you'll want to compare the 2019 data with the 2014 data, because there won't be any overlapping collection years between these 2 datasets. We tend to pull 2019 (most current), 2014 (5 year without overlapping collection years) and 2000 data for these types of projects.
The good news is that there won't be a lot of change between 2019 data and 2018 data, because the estimates are based on 4 of the same survey years and only have 1 unique survey year. Most of our clients wait 2 to 3 years before buying a more current dataset. The only clients who get year over year updates are those clients, who for marketing purposes, have to be able to say "we are using the most current US Census data." So marketing drives the data update decision rather than changes in statistics for these clients.