The liberal news media site Vox claims that a recently released data base shows that teachers in the U.S. are underpaid. It lets users look up the alleged underpayment level for each state.

“Your state’s teachers are underpaid,” the Vox article declared. “Find out by how much.”

In its entry for Michigan, the website states, “It looks like all salaries have been increasing, but that’s a bit misleading because we have to adjust for inflation. This will tell us if teachers in your state have actually been getting raises or not.”

Vox claims that Michigan teachers have had their pay cut by 12.1 percent over a recent 15-year period. The site claims that since 2010 (the year voters elected a GOP governor and Legislature) pay for Michigan’s teachers has been cut 4.2 percent. Vox uses data from the National Education Association annual surveys.

But Vox makes the inaccurate assumption that the statewide average salary of all Michigan teachers is an indication of whether pay levels for individuals are increasing or decreasing.

They are not. This is especially true in a state like Michigan, where the highest-paid teachers are those who have the highest seniority. The compensation of virtually all conventional public school teachers in this state is specified in union pay scales in each district that are based on years of experience and the number of extra academic credits accumulated.

State records show that the actual salaries earned by most Michigan teachers with less seniority – those who have not reached the top of the union pay scale — do benefit from periodic pay hikes. The exceptions occur among the handful of school districts that are in dire financial situations.

For example, the average teacher salary at Troy Public Schools was $74,459 in 2016-17, according to the Michigan Department of Education. The average amount was $72,871 in 2013-14, which when adjusted for inflation would be $75,650 in 2017 dollars.

By Vox’s rationale, that would mean Troy teachers have taken a pay cut. Except, that’s now how it works.

Changes in a particular district’s average teacher salary is mostly a product of how many highly paid, high-seniority teachers are retiring and being replaced by newer teachers lower down on the union pay scale.

At the top of the pay scale, a Troy teacher makes $91,250. A new hire starts at $43,000. In 2017, Troy advertised for nearly 90 open teaching jobs.

And Troy teachers received raises from 2013-14 to 2016-17, as spelled out in their union contract. A Troy teacher with a bachelor’s degree who started in 2012-13 would have made $41,297 that year, which by 2016-17 would have risen to $50,900.

Vox reporter Alvin Chang said he thinks average salary data does capture general trends going on in the country.

In an email, Chang wrote: “I think your anxiety with the data isn't quite framed correctly. For example, when we think about average incomes of Americans, we don’t say: This is meaningless, because what if a retiring worker is replaced by a young worker, which brings down the average.”

“Rather, I think the question is: Have the demographics of teachers changed drastically in the time frame the data covers? And the answer is: Kind of. The average age nationwide has stayed about the same (and same for most states), but there are a few more teacher under 30, as well as a few more teachers over 50, and so fewer teachers in that 30-49 age range. At the end of the day, the median age evens out,” Change wrote.

He continued: “So in this case, average salaries tell us quite a bit, and I have a subsequent story looking at health care premiums, which fills out the picture a bit. Does this tell an exact story about every state and every school district? No. But does it capture general trends in each state, as well as nationwide? I believe it does.”

There is a website that tracks salaries of nearly all public sector employees in Michigan. OpenTheBooks.com is a nonprofit whose mission is to “to capture and post all disclosed spending at every level of government.” The nonprofit has posted several years’ worth of salary data for almost every government worker in Michigan and other states.