Studies are like snowflakes — no two are alike

Aug. 18--It seems that at least once a week I receive an email touting some supposed study showing how high or low Caldwell County or one of its municipalities ranks in something.

All of these "studies" also come out every year, so now, into year seven of being the editor at the News-Topic, I've seen many of them before.

One email that came this past week was a "reminder" that on Aug. 14 I had been sent a link to a "study" by a website called SmartAsset.com that ranked Sawmills as the fourth most affordable place to live in North Carolina. And actually the same study had been sent to me April 15 as well. The person sending the email really, really wants us to write about that ranking.

Problem is we've already written that story -- the last time it came out.

In sorting through my email to find out when that was, though, I came across two different "studies" from two other websites showing both the most affordable and least affordable places to live in North Carolina -- and Sawmills didn't appear on those at all. Not most or least.

It's not Sawmills' fault.

All three of these purport to show the most/least affordable places to live based on housing costs.

The two studies that don't list Sawmills, from HomeArea.com and UnitedStatesZipCodes.org, both base their rankings on data from the U.S. Census Bureau's 2017 American Community Survey. They both compare an area's housing prices with the median income to determine how long it would take to pay off the loan to buy a house there.

HomeArea.com's top five most affordable: High Point, Fayetteville, Concord, Gastonia, Winston-Salem.

UnitedStatesZipCodes.org's top five: Maury, Fairfield, Marston, Polkton, Morven.

The key difference between these two seems to be that HomeArea.com is evaluating large areas, while UnitedStateZipCodes.org is analyzing individual ZIP codes. Sawmills doesn't have a ZIP code -- it's divided between the Hudson and Granite Falls ZIP codes, so it never stood a chance of making that study.

But no part of Caldwell County appears anywhere in the ZIP rankings. The reason for this is implied in the study's methodology: It lists only ZIPs with "a low margin of error." The way you get a low margin of error is by having a lot of data -- in this case, house sales. But in Caldwell County, there are never a large number of homes bought or sold in a single year. Therefore, all of our ZIPs probably have a relatively high margin of error.

HomeArea.com has omissions of its own. For one, no part of the Hickory region -- known by the Census Bureau as the Hickory-Lenoir-Morganton metropolitan statistical area -- is listed. In fact, only 14 places statewide are listed. Also missing are the Burlington and New Bern metro areas. The site's "About the rankings" explanation doesn't say how it chose its 14 places.

Back to SmartAsset. I'll give it credit for one thing: It cites a lot more sources. It includes the exact same American Community Survey data as the other two but also data from Bankrate, the National Association of Insurance Commissioners and "government websites" that it doesn't name. Besides housing costs and income, it factors in property taxes, insurance costs and "affordability," whatever that means.

But let's circle back to the one factor that the ZIP code study probably got right: margin of error.

All of SmartAsset.com's most affordable are very small towns. The question is how many house sales are included in this data? A small sample size can lead to large errors. If you have just a handful of sales in a year, and they all happen to be smaller, older houses, your area looks a lot more affordable than it would in a year when several larger, newer houses sell. A large number of sales tends to even that out.

That certainly doesn't mean that Sawmills is not among the most affordable places to live in North Carolina.

It just means that you can craft a study to show anything you want if you mix the right set of statistics.

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