I don't know where data on this gets published. I know a lot of data is analyzed from buying habits and a result of this is that retailers can know a lot of things about its customers which is why consumer data is so valuable (anecdote - companies can know a woman is pregnant before she does). I don't want to discount the kind of information retailers and manufacturers have about us. Insurance companies have a similar process using
Predictive Analytics though it's not mature in the same way as it is in retail. That said, it's one thing to use the data to determine preferences but it's another thing to glean changes in those preferences over time. This seems (this is my subjective opinion) less likely as the data is probably noisy and is based on certain implicit assumptions about a buyer rather than than explicit facts. You might buy a ranger jersey or tickets as a gift for family , friend, coworker or yourself. (I have Yankee tickets but I'm not a Yankee fan). You're buying socks and detergent for your family. You also have the problem of needing to adjust for glory supporters and people changing their "fandom" depending on how teams are performing.
When I was a kid I'd watch my teams and could only watch superstars from other teams during the all star games. With cable and streaming packages I can watch whatever game I want. It seems there's less loyalty to teams than to players in the younger generation (again, my subjective opinion). But what's changed over the years (in NYC at least) is the number of out of towners who work here. Maybe half of my coworkers (who follow sports) are fans of teams from outside the tri-sate area. We just hired a philly fan.
Not really published, as it's a bit too boring for the average person, though in the past it has tended to jive with different polls and surveys that outlets and other entities have conducted. Generally speaking there's traditionally been a clear pattern from multiple sources, using multiple methods.
Now, could it all be bunk? Sure. But I've generally found it to be true and supported.
However, the way younger fans change the findings will be interesting. As you said, there are more options that ever before and there's also been a growing trend for younger generations to switch allegiances a little more often.
While there's always been an element of kids gravitating towards teams that were popular or successful during their formative years (say the Steelers, Cowboys, Bulls, Yankees, Michigan, Red Wings, etc.), we've been finding that there's more shuffling than there used to be. A lot of fans 35 and under have shown an increasing tendency to switch alliances and spending more than previous generations.
The way younger fans describe their experiences has also changed with sports and entertainment as well, with more fans expressing a desire to be part of an "experience" than necessarily being part of a grouping. In other words they enjoy going to the concert, more than they necessarily enjoy the band. They enjoy going to a game, and enjoying the festivities, more than they have a vested interest in the team or even the sport.
So in that regard, the way different leagues and companies approach their audiences will continue to evolve. What impact that has on more traditional groupings is still a bit of an unknown.
But it's important to note that sometimes these findings can be construed different ways.
For example, let's say that 60 percent of Rangers fans are also Giants fans, and 40 percent root for the Jets (yes I know the real percentages wouldn't be so clean, but this is for demonstrative purposes). You could clearly argue that the Rangers have more crossover with the Giants than the Jets. You can even (potentially) claim that the Rangers fans were 50 percent more likely to root for the Giants than Jets. But what gets overlooked is that the number of Rangers who root for the Jets is still a significant number.
So just because it's not
as common to find a Rangers-Jets pairing, as it is a Rangers-Giants pairing, it's still not an
uncommon occurrence. You're still talking about millions of consumers.
Just something for people to keep in mind when looking at the context of what we're discussing.
Now how those combinations are constructed is a bit more complicated. However, as of several years ago, at least in the NY market, there was still a significant carry-over from the old geographic allegiances and it was surprisingly resilient to team performances, geographic changes, and (at the time) technology and changes in how content was consumed. In short, the average fan was still primarily driven by family alliances --- some of which predated their existence. Someone born in 1986 would have no memory of the Islanders dynasty, or the Jets playing in Queens. But there's a good chance they were brought up in a household that remembered.
Fast forward 33 years later, and they have a kid who is 8 years old who roots for those teams based off events that were two generations before they were born. At least that's what different data has continued to point to thus far.