In recent years commentators have increasingly weighed in on the greying of Congress. In 2010 The Hill noted that “the oldest Congress ever is getting hip to new technology.” NBC boldly declared that on Capitol Hill, “old is in.” Most observers attributed this to the power of incumbency, and to legislators deciding to stay in office longer. As Slate’s Explainer explained, “Dips and surges in the age of our legislators probably have less to do with our attitudes toward the elderly than with views about incumbents.”

Indeed, the historical trend is undeniable: the average age of Congressmen has increased steadily over the centuries. In the early 1800s the average Representative or Senator was in his mid-40s. Fast forward to today, when the average Senator is nearly twenty years older - at 62 - and the average Representative is nearly 15 years older at 57. Want to find out how old your state's Congressional delegation is? Find out with these interactive maps.

While incumbency undoubtedly plays a role here, there’s an even larger – and simpler - factor at play: Congress has aged because the nation has aged with it. The chart below shows average age in the House and Senate since 1900, and adds the median age of the total population over the same period.

Average age in the House and Senate was flat for much of the century, before dipping in the 1970s and rising steadily thereafter. But the median age has been on a steady rise all along, with a small dip from the 50s to the 70s caused by the baby boom. In fact, the gap between the median age and congressional age actually shrunk over that time period, implying that Congressmen are actually younger relative to the rest of the population today than they were 100 years ago.

A clearer way to express this would be to look at the ratio of average Congressional age to median age, as in the chart below.

Here the downward trend is even more pronounced – today the average Congressman is roughly 1.5x as old as the average U.S. citizen. Again, the ratio is much smaller than it was in the early 1900s, when the average Congressman was anywhere from 2 to 2.5 times as old as the average citizen. If that same ratio held true today, the average Senator would be 93 years old! The actual Senatorial average of 63 is downright sprightly by comparison.

More to the point, this chart shows that in recent years the ratio of Congressional age to median age has been flat – today, Congress is older than the rest of us by the same amount as it was ten years ago. In the end, it’s clear that Congressmen are indeed getting older – but so is everybody else.