Over the last decade and a half or so, several MLB stadiums have shrunk, and several new ones have opened at smaller capacities than their predecessors. But why is this? Well, the simplest answer is lower demand. But in reality, there are several factors that go into this, making it a little bit more complex than what you see on the surface. This is why MLB stadiums are shrinking.
Going into the 1990s, MLB stadiums began to become an experience and not just a place to attend a game. With the new retro classic style ballparks such as Camden Yards and Jacob’s Field, you weren’t just going to a game, you were going for the stadium experience. Improved clubs, luxury boxes, restaurants, and better aesthetics made the experience miles ahead of what was before.

The building boom of new ballparks in the 90s and early 2000s would pay off at the gate, with attendance jumping from the low 20,000 in the late 1980s league-wide to the high 20,000 and low 30,000 in the late ’90s and well into the 2000s. New ballparks were definitely part of it. Teams such as the Cleveland Indians, Baltimore Orioles, Colorado Rockies, and later on, the Philadelphia Phillies would have multiple seasons in a row of 40 plus thousand fans per game after or shortly after their new ballparks would open. There were also others drawing quite well during this time.
However, as the shine wore off of these new ballparks and overall interest in Major League Baseball changed, a time would come leading up to today where attendance has significantly dropped. So much so that thousands in seats and capacity have been taken out of stadiums. Progressive Field, which opened at a capacity of around 43,000, now holds just 35,000, a drop of around 8,000 capacity. Camden Yards, which opened to a capacity of just under 49,000, now holds 45,000, a loss of nearly 4,000 in capacity. Coors Field would remove over 3,000 seats, though its overall capacity would remain the same with standing room. Others would chip away seats as well.

But the question is why? It doesn’t really cost any extra money to have empty seats in your ballpark; they’re already there whether there’s demand or not. So why get rid of them? This brings in the discussion of dynamic pricing, now something used today at nearly every ballpark. It was basically a foreign concept 30 years ago. If a team can simply get rid of supply, they can inflate the value of seats. Say you sold 15 seats at $10 a piece, that would give you $150. But if you could sell one at $15 a piece or even more than that because of high demand and low supply, you either broke even or made even more money.
Then also comes the idea of money spent within the ballpark. In all likelihood, the people sitting in the lowest-priced seats will spend the least at a game. But if the space of those seats can be created to make areas that increase the chances of people spending more money within the ballpark, particularly by those that will spend more, whose seats are in the higher-priced sections, then much of that lost gate money can be made up, especially on the many occasions where the far away and low price sections won’t sell anyway, as is the case with the Rockies.
They got the best of both: more places and opportunities for people to spend money while not losing any actual capacity. Then there’s the aesthetic factor. Whether it’s for fans, the team, or for the television broadcast, no one wants to see sections upon sections, game after game, of empty seats. It just gives off an atmosphere of low interest.
So today, with less fixed pricing, increased opportunities for alternative revenue, and the desire for a better atmosphere, existing ballparks have shrunk, and new ones typically are much smaller than their predecessors. Such as the Texas Rangers Globe Life Field holding roughly 9,000 less than Globe Life Park, its predecessor. So yes, while overall demand is the biggest factor in all of this, the way and method teams use to generate revenue and how it’s changed have perhaps become just as important.