With only four exceptions, every new Congress that arrived in Washington from 1901 to 1953 saw one party controlling the House, the Senate and the White House. Unified government was the norm. That held in the 1960s, too, with Democrats not only holding unified control of Washington but even a 60-plus-vote majority in the Senate.

Since then? Unified governments are the exception. Since the new Congress of 1969, arriving in Washington with Richard M. Nixon, there have been eight new Congresses in which one party has held unified control — but in 2001, a senator’s defection quickly meant that Republicans lost that advantage.

This point is better made visually, as are most points.

Tacked on at the end there is the newly christened 116th Congress, established this week and bringing to an end a brief period in which Republicans had control of both chambers and the White House.

The question that naturally follows is how this will affect the effectiveness of Congress. It makes intuitive sense that when one party controls the entire apparatus for passing legislation, more legislation would be passed. As it turns out, though, it’s not quite that neat.

GovTrack.us has data on the number of new laws enacted in each Congress since 1973. The peak over that period came in the 95th Congress, which took office in 1977 with Democratic President Jimmy Carter, a Democratic majority in the House and a Democratic majority in the Senate that topped 60 votes. Evidence, it would seem, for the utility of unified government. But, then, only slightly less legislation was passed in the four years prior.

It’s murky. Since 1973, Congresses in which there was unified party control enacted an average of 541 new laws. Congresses in which there was a divide passed an average of . . . 533. That’s a subtle distinction.

A good recent example is 2007, when Democrats who had won majorities in the 2006 midterms seized control of Capitol Hill. The number of laws enacted in that Congress trended downward, but it had in the 2005-2006 Congress, too.

There are any number of complicating factors that undergird this, of course: the willingness of either party to compromise, the willingness of a president to forge bipartisan agreements, the strength of either party’s majority in the House and the Senate. The most recent Congress had a very narrow Republican majority and a fractured Republican caucus in the House, which, combined with President Trump’s generally lackadaisical approach to policy, certainly didn’t help things move forward.

Interestingly, as GovTrack noted in an article wrapping up the most recent Congress, a “handful of new laws were passed with more Democrats in support than Republicans, including major federal funding bills . . . and many laws contained provisions originally authored by Democrats.” In a news release, the site noted that “[s]ome of the most significant bills enacted in the last two years were supported more by Democrats than Republicans.”

In other words, even with unified control of Congress, Republicans got more done, thanks in part to working with Democrats, a process that is now the default standard for effectiveness. Meaning, to put a fine point on it, that the incoming Congress might not be any less effective at enacting legislation as the one that just ended.