# Unusual Discrepancy between One and Five year Results

I've run into a bit of a conundrum when comparing one and five year results for Table B25038 TENURE BY YEAR HOUSEHOLDER MOVED INTO UNIT.

I am comparing values for the City of Cambridge, Massachusetts after calculating the percentage of householders who moved into their units in the prior two years, the most recent category provided.

For the period 2017 through 2021 I found the following proportions using one year data starting with 2017: 44%, 31%, 44%, null (no table for 2020), and 45%.

From the 2017-2021 ACS the same table generates the value of 17% for the same category.

Comparing published values, the 2021 ACS reports that 23,719 householders moved into their unit since 2019 where as the 2017-21 five year ACS reports 8,192. Similar discrepancies exist for 2017, 2018, and 2019.

While I do not expect one year and five year ACS data to match or have a simple mathematical relationship to one another, the level of the discrepancy is unusual in my experience.  Have others had similar observations?

Parents
• David

"Not to be too humorous but one question could be how many garbage trucks you need on September 2nd to pick up all the junk that people put out on the sidewalk over the weekend."  As it happens, this question did originate from our solid waste staff, who want to get a handle on the number of new households needing education about trash disposal and recycling each year.

I somehow missed your original post.  I assume that your edit is found in the first two paragraphs of your post.

This could indeed be one of the consequences of the disruptions to data collection caused by Covid, though I suspect something else is afoot.  I am aware that comparing overlapping ACS estimates is fraught.  That aside, I would not expect to see differences of the magnitude seen here.  One aspect I had not paid enough attention to until now is the most recent category in table B25038 varies and might start 0, 1 or 2 years in the past.  Here is a table comparing most current values from the 2017-21 ACS and the preceding one year ACS tables:

 ACS Data Set Most Recent Category Years Elapsed Count 2017-21 Moved in 2019 or Later 2 8,192 2021 Moved in 2019 or Later 2 23,719 2020 -- -- -- 2019 Moved in 2019 or Later 2 20,931 2018 Moved in 2017 or Later 1 14,369 2017 Moved in 2015 or Later 2 19,666

Here is a similar table from the 2014-18 ACS, so we can rule out Covid effects:

 ACS Data Set Most Recent Category Years Elapsed Count 2014-18 Moved in 2017 or Later 1 3,747 2018 Moved in 2017 or Later 1 14,369 2017 Moved in 2015 or Later 2 19,666 2016 Moved in 2015 or Later 1 14,793 2015 Moved in 2015 or Later 0 3,487 2014 Moved in 2010 or Later 4 22,274

I don't think the changing number of "years elapsed" account s for what I'm seeing but it certainly complicates the picture.

• David

"Not to be too humorous but one question could be how many garbage trucks you need on September 2nd to pick up all the junk that people put out on the sidewalk over the weekend."  As it happens, this question did originate from our solid waste staff, who want to get a handle on the number of new households needing education about trash disposal and recycling each year.

I somehow missed your original post.  I assume that your edit is found in the first two paragraphs of your post.

This could indeed be one of the consequences of the disruptions to data collection caused by Covid, though I suspect something else is afoot.  I am aware that comparing overlapping ACS estimates is fraught.  That aside, I would not expect to see differences of the magnitude seen here.  One aspect I had not paid enough attention to until now is the most recent category in table B25038 varies and might start 0, 1 or 2 years in the past.  Here is a table comparing most current values from the 2017-21 ACS and the preceding one year ACS tables:

 ACS Data Set Most Recent Category Years Elapsed Count 2017-21 Moved in 2019 or Later 2 8,192 2021 Moved in 2019 or Later 2 23,719 2020 -- -- -- 2019 Moved in 2019 or Later 2 20,931 2018 Moved in 2017 or Later 1 14,369 2017 Moved in 2015 or Later 2 19,666

Here is a similar table from the 2014-18 ACS, so we can rule out Covid effects:

 ACS Data Set Most Recent Category Years Elapsed Count 2014-18 Moved in 2017 or Later 1 3,747 2018 Moved in 2017 or Later 1 14,369 2017 Moved in 2015 or Later 2 19,666 2016 Moved in 2015 or Later 1 14,793 2015 Moved in 2015 or Later 0 3,487 2014 Moved in 2010 or Later 4 22,274

I don't think the changing number of "years elapsed" account s for what I'm seeing but it certainly complicates the picture.

Children
No Data