Call it a sign of the (run)times.

If it feels like feature films are featuring a lot more film these days, you’re not crazy. Data visualization wiz Randal Olson set out to use hard numbers culled from IMDB to answer one simple question: “Are movies really getting longer than they used to be? Or are a few outliers–like The Lord of the Rings series–skewing our perception of what’s really going on?”

As Olson shares in his blog post presenting the data, he plotted the runtimes of the 25 most popular films per year from 1931 to 2013. Then, he donned his data-analysis cap to speculate on why the graph reflects net growth over the decades, with a few peculiarly timed dips.

For the sharp rise in length from 1931 to around 1960, Olson gives this straightforward explanation:

“With the introduction of the television in the 1930s and 1940s, the movie industry suddenly had a competitor. In response … Feature films gained an extra 30 minutes … which set the standard in film for the next 50 years, and eventually led to the blockbuster phenomenon.”

And that numerical nadir after the ’60s?

“The only explanation I can think of,” Olson writes, “is the videotape format war in the 1970s, where VHS and Betamax were battling it out to become the dominant movie format.”

As he points out, the Brobdingnagian blockbusters that today’s viewers associate with those “few outliers” (hobbit-filled or otherwise) are actually just “keeping with the status quo established in 1960.”

To corroborate his assessment, Olson takes readers on a brief tour of Hollywood’s longer classics.

“We may have a few lengthy blockbusters nowadays,” he concedes, “but they sure don’t stack up to much when compared to 20th century epics like Gone with the Wind (1939, 223 mins), The Ten Commandments (1956, 220 mins), and Lawrence of Arabia (1962, 216 mins).”

Compare those figures to Titanic (194 minutes) and The Revenant (a meager 156), and it’s clear that while new theatrical releases have gotten longer over time for those of us born between 1970 and about 1995, the typical runtimes in theaters now have the ’60s to blame.

To read Olson’s full analysis, check out the original post on his website.

(And of course, it’s worth noting that this US-centric graph ignores one enormous film industry that would disrupt all of Olson’s results: Bollywood.)