Major League Baseball is eager to speed up our national pastime. In the past few offseasons, MLB has tried to combat the slowing pace of play by targeting pitching changes, intentional walks and mound visits. But another significant culprit behind the sport’s sluggish pace of play may be something that no pitch clock or simple rule change can fix: the foul ball.

The number of foul balls has increased by 11.98 percent from 1998, when baseball expanded to 30 teams, according to a FiveThirtyEight analysis of Baseball-Reference.com data. There were almost 14,000 more foul balls last season than there were 20 seasons earlier. In 1998, 26.5 percent of all strikes were foul balls. That share increased to a record 27.9 percent of strikes in 2017 and 27.8 percent last season, the top rates since pitch-level data was first recorded in 1988.

Overall, there were 26,313 more pitches in baseball in 2018 (724,447) than in 1998 (698,134). That’s the equivalent of adding 88 games, or roughly a week, to the schedule. A record 3.9 pitches were thrown per plate appearance in the 2017 and 2018 seasons, according to Baseball-Reference.com, up from 3.73 pitches per plate appearance in 2002 and 3.58 in 1988. And about half of the growth in total pitches can be attributed to foul balls.

For the first time since pitch-level data has been recorded, there were more foul balls than balls put in play in 2017 — and that trend continued in 2018.

There’s no doubt that baseball is slowing down, which is a concern for the commissioner’s office as the game competes against more free-flowing sports like soccer and basketball. “Pace of game is a fan issue,” MLB commissioner Rob Manfred told reporters last February. “Our research tells us that it’s a fan issue. Our broadcast partners tell us it’s a fan issue. Independent research that our broadcast partners do confirm the fact that it is a fan issue.”

Sports Illustrated reported that last October’s World Series saw an average of four minutes and 26 seconds between batted balls put in play — which was 40 seconds greater than the 1998 series. In the 1998 season, there were 5.05 pitches per ball put in play for a recorded out or hit. Last season? 5.73 pitches.

So why are there more foul balls?

White Sox first baseman Yonder Alonso says there’s one clear factor in the increase of foul balls: The quality of pitchers keeps improving.

“As a hitter, the game is evolving to be tougher,” Alonso said. “There are times when you are going to have to waste a pitch. And there are times when you are not necessarily trying to waste a pitch but it’s an emergency hack, an emergency swing. You are swinging very late just hoping for another another swing, another pitch.”

Pitching velocity has increased nearly every season since 2008, when pitch tracking began in all ballparks, and more breaking balls are being thrown as fastball usage declines. Generally, hitters perform better — and pitchers perform worse — when fastballs are thrown. The game has never been more specialized, with bullpens accounting for a record 40.1 percent of innings last season. Relievers typically throw with more velocity and strike out more batters, meaning that batters are facing high-quality pitching from relievers even earlier in games.

Moreover, the penalties for hitting a foul ball have also declined.

While fans have a better chance than ever at grabbing a free souvenir, fielders do not. In 2003, there were 4,372 foul outs. That number has fallen off dramatically, reaching a record low 3,262 in 2016 and hitting 3,450 last season.

An increase in foul balls and a decline in foul outs may seem paradoxical, but the reason is simple: Playing surfaces are shrinking. In comparing 21 current stadiums with their immediate predecessor, FanGraphs found that fair territory had decreased by 1.4 percent, but foul territory decreased by 20.5 percent, or about 5,500 square feet on average.

“You use that to your favor,” Alonso said of fouling off pitches at stadiums with less playing surface.

While so much of the focus has been on pitchers slowing the game, it might be hitters that actually deserve the lion’s share of blame: from routinely leaving the batter’s box, to trying to increase pitch counts, to increasingly being unable to put the ball in the play. But it’s easier to try to speed up the game with a clock on the pitcher than to try to reduce strikeouts or limit foul balls.

Baseball has tackled foul-ball issues before: In fact, it was one of the original pace-of-play frustrations. In 1900, Phillies outfielder Roy Thomas was so adept at fouling off pitches to draw walks or spoil quality offerings that Reds pitcher Bill Phillips reached his breaking point and punched Thomas after he had fouled off a dozen pitches in one at-bat. Phillips’s antics, according to baseball historian John Thorn, were a contributing factor in MLB’s decision to begin penalizing foul balls as strikes the following season.

But there’s been no rule change since, and the foul ball continues to slow the sport — while the game’s decision makers look elsewhere to hasten play.