Congress returns from vacation in September, and while most of lawmakers’ agenda will be about tax reform, the budget, and the debt ceiling, Calcbench decided to take one last look at the big issue from earlier this year: healthcare.

Specifically, we wanted to dig into the financial picture of the largest for-profit health insurers in the country. We last examined this issue one year ago. We found that from 2013 to 2015, the 10 largest insurers had seen brisk growth in both total revenue (from $354.2 billion to $457 billion) and operating income ($21.6 billion to $27.5 billion).

So what’s changed in the last 12 months? And can Calcbench databases shed any additional light on the group’s overall financial performance?

Using our Data Query Tool, we pulled total revenue, operating expenses, and operating income for the remaining nine large health insurers we looked at last year. (HealthNet was acquired by Centene Corp. since then, so total group revenues and expenses remain the same, just allocated to nine firms instead of ten.)

We found this:

In pure dollar terms, those numbers don’t look so bad. Revenue rose faster than operating expenses; profits went up year over year for four consecutive years. That can’t be terrible, right?

In pure dollar terms, no. But look more closely at the changes from year to year within those three columns, and a different picture emerges. Maybe those insurance executives complaining about the difficult operating environment for health insurance aren’t entirely off-base after all.

Start with operating income. Yes, it rose 30.3 percent from 2013 to 2016. But when you examine the year-over-year growth in operating income, you see this:

Well, if you’re the CFO at a large insurer— yuck. That deceleration in growth does you no favors with your budget, strategic plans, or investors.

Then we looked at the year-over-year change for all three categories. The results are below.

Oh dear. That 2016 slowdown in revenue growth is not a welcome development at all. Little wonder, then, that the sector also has been cutting operating expenses (severely, in the last year).

Indeed, if we go back to our first table at the top, and include operating income as a percentage of revenue, you might even feel a tinge of sympathy for those CEOs and CFOs. Take a look.

A drop of 36 basis points might not seem like much, but in relative terms that’s a slowdown of nearly 6 percent— a much steeper decline than one might assume at first glance. And that margin has declined for three consecutive years.

Food for thought, as Congress reconvenes after Labor Day.