The Dead Ball Is Back

Home Runs Vanished and Nobody Said Anything

In 2019, MLB hitters launched 6,776 home runs. It was the highest total in league history. The ball was carrying. Everyone knew it. Pitchers complained. Physicists measured the seams. The league acknowledged what it called "inconsistencies" in the manufacturing process.

By 2022, the total had dropped to 5,215. In 2025, it fell further to an estimated 5,180. That is a 24% decline from peak to present. The hitters got stronger. The bats stayed the same. The ball got quieter.

League-wide HR/FB rate tells the clearest story. It peaked at 15.3% in 2019, fell to 12.1% in 2022, and sat at 11.8% through the first half of 2025. Same swings. Same launch angles. Different outcomes.

Four Ball Changes in Six Years

MLB uses Rawlings baseballs manufactured at a single facility in Costa Rica. The specifications are tight: weight between 5.00 and 5.25 ounces, circumference between 9.00 and 9.25 inches. But within those tolerances, small changes to seam height, core composition, and the coefficient of restitution (COR) alter how far the ball travels.

The 2020 drop coincided with a league-acknowledged ball change. Rawlings adjusted the seam height to reduce carry. The 2022 drop accompanied a second adjustment that tightened COR tolerances. The 2024 and 2025 balls appear to have slightly higher seam heights again, based on independent lab testing by Meredith Wills and other researchers who purchase game-used balls and measure them.

MLB has never formally announced a ball change except retroactively. The 2019 "inconsistencies" were acknowledged only after a full season of record offense. Each subsequent adjustment has arrived without press release or rule change. The ball gets quieter. The league says nothing. The data says everything.

How a Millimeter Changes a Season

Seam height controls drag. Higher seams create more turbulence as the ball moves through air, increasing drag and reducing carry. A seam height increase of 0.01 inches (roughly 0.25 mm) reduces fly ball distance by approximately 2 feet. On a 380-foot fly ball, 2 feet is the difference between a home run and a warning-track out.

COR measures how much energy the ball retains after impact with the bat. The MLB specification allows COR between 0.514 and 0.578. A ball at 0.578 leaves the bat approximately 2 mph faster than a ball at 0.514. Over the flight of a fly ball, 2 mph of exit velocity translates to roughly 8 feet of distance.

The humidor program complicates the picture further. MLB expanded humidor use from one park (Coors Field) to all 30 ballparks between 2018 and 2022. Humidors store balls at controlled temperature (70°F) and humidity (50%). Humid balls are heavier and have lower COR. The humidor expansion alone accounts for some portion of the home run decline, independent of any manufacturing changes.

The Data Always Catches the Ball

Every time MLB changes the ball, a signature appears in the Statcast data. Exit velocity stays constant (hitters swing the same), but distance on fly balls drops. The gap between expected home runs (based on exit velocity and launch angle) and actual home runs widens.

In 2019, actual home runs exceeded the Statcast model's expectation by 496. The ball was carrying beyond what exit velocity and launch angle predicted. By 2025, the gap reversed to -570. Hitters are hitting the ball harder than ever (89.1 mph average exit velo, up from 88.4 in 2019) and getting fewer home runs for it. The only variable that changed is the ball.

Hitters Pay the Price MLB Sets

When the ball changes, some hitters lose more than others. Power hitters who relied on fly ball distance get penalized disproportionately. Contact hitters who drive line drives are barely affected. The dead ball redistributes offensive value away from power and toward contact.

Between 2019 and 2025, the average isolated power (ISO) for hitters with a fly ball rate above 40% dropped from .198 to .168. For hitters with a fly ball rate below 30%, ISO was nearly unchanged (.142 to .139). The ball change hit fly ball hitters with a 15% power reduction while contact hitters lost almost nothing.

This matters for contracts. A team that signed a fly ball hitter to a long-term deal in 2019 based on his home run output is now paying for production the ball no longer allows. The hitter makes the same contact. The ball lands 8 feet shorter. The home run column shrinks. The contract stays the same.

Should MLB Tell Us When the Ball Changes?

Four times in six years, MLB altered a core piece of equipment without formal announcement. Each change shifted offensive outcomes, affected player valuations, and changed which hitters looked productive. Fans noticed. Analysts proved it. The league stayed quiet until the data made silence untenable.

Other sports disclose equipment changes. The NBA publishes ball specifications when it changes manufacturers. The NFL announced its switch from leather to composite balls and back. Tennis governing bodies publicize changes to ball compression and felt composition. MLB treats its ball specifications as operational details rather than competitive information.

The integrity issue is straightforward. If the ball changes and nobody knows, contracts signed based on pre-change performance are mispriced. MVP votes cast based on counting stats are distorted. Hall of Fame arguments that compare eras become meaningless without adjusting for which ball each player hit. The records and the money flow through a variable that one organization controls and declines to disclose.

Sources & Data

Jesse Walker

Jesse Walker writes about baseball through data. He played outfield in high school, found his real position behind a spreadsheet, and hasn't stopped building models since.