What’s causing sales for recent big films to drop sharply after their first weekend?

“The Amazing Spider-Man 2,” “Godzilla” and “X-Men: Days of Future Past” have all enjoyed big opening weekends in the last month, each earning between $90 million and $95 million in just their first three days.

But all of these movies have something else in common: a precipitous drop-off in ticket sales the following weekend.

“Spider-Man 2” saw its numbers drop 61% from its first weekend. “Godzilla” plummeted 67%. This past weekend, “X-Men” tumbled 64% from figures it posted in its first three days.

The conventional wisdom for most blockbuster movies has been that a drop of more than 50% is disappointing. If the number rises above 60%, the drop begins to look like a cliff dive.

It’s part of what might be called a one-and-done moviegoing culture — films that, for all their firepower, quickly lose their dominance at the box office.

“It’s an interesting thing, and hard to figure out what’s going on,” said Bruce Nash, who runs Hollywood data-analysis site the Numbers. “Is it that moviegoers are just moving on to the next shiny thing, or that these movies just have a very narrow appeal that doesn’t go beyond their opening weekend?”

The so-called summer season that runs from May through July is not one for slow-burn hits. Unlike the fall and winter, when hit films can see box office revenue barely decline for weeks or even months — “Gravity” was a prime example last fall — movies flame out much faster this time of year.

But even by the adjusted standards of summer, the 2014 numbers are notable.

In recent years, far bigger openings have dropped less, and smaller openings have dropped considerably less.

In 2013 “Iron Man 3,” which opened to a gargantuan $174 million, still managed to fall only 58% in its second weekend. “Star Trek Into Darkness,” which opened to a more modest $70 million, dropped just 47%.

At the very least, experts said, these 60% to 70% drops should be happening occasionally, not all the time.

If this year’s drops seem sizable compared with last year, they appear downright precipitous if you go further back. The first “Star Trek” in 2009 opened at $75 million — yet fell only 43% in its second weekend.

The biggest May opener in 2004 was “Shrek 2,” which opened to a hefty $108 million — yet fell just 33% the following weekend.

One Hollywood veteran who requested anonymity so as not to appear to be criticizing colleagues and competitors said that new movies may simply not be built to last; these branded action adventures are a kind of “empty-calorie cinema” that doesn’t inspire long-term moviegoing.

Others have pointed to the advent of digital platforms and the ease with which these movies can be seen elsewhere. If one isn’t a part of the opening-weekend phenomenon in theaters, better to wait for the movie on Redbox, Netflix or cable on-demand.

The economics have studios concerned. Customer retention is a key benchmark for any business, and if the industry cannot get people to see a movie a week after it’s out, it’s not only losing valuable box-office dollars but also losing a capacity for relevance. If studios can’t get audiences to remember these movies after just seven days, what happens when a sequel is supposed to hit in two years?

In contrast to television, movies aren’t generating the kind of ongoing water-cooler buzz that makes screen entertainment fun in the first place. A few summers ago, films hung around for at least a few weeks, allowing us to catch up and discuss without feeling like we’re picking at stale bread.

Next weekend will bring another test: the follow-up weekend to the seemingly strong $70-million opening for a certain Angelina Jolie fairy tale.

“We’ll see if ‘Maleficent’ can have a good hold. It just might,” Nash said. Or it might not, because audiences will have moved on to “The Fault in Our Stars,”

the next big shiny movie thing.

steve.zeitchik@latimes.com