Mr. Fullerton said he had then learned that since 2009, the shares of some publicly traded companies with sport sponsorships had outperformed their industry counterparts. He declined to provide supporting data.
To embody that theory in a financial instrument, the partners turned to the Global Index Group in Seattle, which helped them create an exchange-traded fund that included dozens of companies with sponsorships with Major League Baseball, the National Basketball Association, the National Football League and the National Hockey League, as well as with individual teams and broadcasters.
The result was the ProSports Sponsors exchange-traded fund. It began trading on July 11 with the ticker, FANZ, and includes names like AT&T, Coca-Cola, Fedex, McDonald’s and Visa.
“We wanted the investor to have an ownership role in their sports,” Mr. Fullerton said.
Unlike mutual funds, which are priced at the end of each trading day, E.T.F.s like ProSports Sponsors can be bought and sold like common stock. E.T.F.s are passively managed, so expenses are generally lower than those for actively managed funds.
ProSports Sponsors has an expense ratio of 0.69 percent. That is relatively expensive for an exchange- traded funds, which often charge about 0.4 percent or less, but cheaper than many actively managed mutual funds.
Investments in E.T.F.s have been growing faster than those in mutual funds as investors become more comfortable with them. According to Morningstar, over the past 18 years, the amount of assets invested in mutual funds has grown 9 percent per year compared with 34 percent growth in E.T.F.s. Matt Hougan, the chief executive of Inside E.T.F.s, which runs conferences and seminars, said that a cumulative $1.5 trillion has poured into E.T.F.s since 2008, while mutual funds have had a net outflow of $100 billion.
“E.T.F.s are like cellphones while mutual funds are like landlines,” he said. “They’re a newer technology, a little cheaper, more tax efficient and more easily tradable.”
The first E.T.F.s tracked familiar indexes like the S.& P. 500. But as their popularity has grown, companies have created a greater variety of funds, including ones based on popular themes as a way of appealing to more investors.
The Point Bridge GOP Stock Tracker E.T.F., (Ticker: MAGA), for instance, includes the stocks of companies that in theory may take advantage of President Trump’s policy priorities. The Obesity E.T.F. (Ticker: SLIM) includes stocks of companies trying to address rising obesity rates, like drug companies that make diabetes drugs. And HACK is an E.T.F. focused on cybersecurity firms.
To create their E.T.F., Mr. Fullerton and Mr. Kozimor listed the names of every official sponsor in the four major sports leagues. Of those 105 companies, they eliminated any that were not listed on an American or Canadian exchange or did not have an American Depositary Receipt.
Credit Jacob Headrick
They then dropped companies that did not have a market capitalization of at least $1 billion or a certain amount of daily trading volume.
That still left dozens of big companies, including Electronic Arts, which makes video games; CBS Corp., which televises N.F.L. games; and Under Armour, which makes gear that athletes wear.
“We created this so you can invest in what you know,” Mr. Fullerton said.
The fund’s start date, July 11, coincided with Major League Baseball’s All-Star game, and it rose 4.7 percent through September. It had about $4 million in assets under management, Ben Jaffe, a fund spokesman, said.
One question for the broader E.T.F. market is whether such funds are being sliced too thin, and whether hyper-specialized ones like ProSports Sponsors are performing well enough to justify higher expense ratios than more traditional funds.
Alex Bryan, who tracks E.T.F.s for Morningstar, does not cover the sports fund because it is so new. But he said he was skeptical that these specialized funds were worth the extra expense. Some fund managers cherry-pick statistics to make the stocks in their funds look like they performed better than those of their peers.
Mr. Bryan added that some managers marketed their niche funds to appeal to investors who wanted to put their money in companies that sold things they understood. But, he said, it was not even clear how much money companies like Geico and Ford Motors earned from being sponsors of pro sports leagues, and therefore the effects of sponsorship on their stock prices were muddy.
It may simply be, he said, that big companies have the money to spend on such sponsorships.
“Firms that have enough money to spend on sport sponsorships may just have more money,” he said. “There doesn’t seem to be any obvious connection between sports sponsorships and stock performance.”
The fund has not been around long enough to know whether it will be a sensible investment, but it certainly provides fans with a familiar choice.
“People get sports, people get advertising,” Mr. Fullerton said. “A lot of products, you need a Ph.D. to understand.”