Jeff and MacKenzie Bezos’s split has created a puzzle for index investors: Who gets their stock in Amazon.com Inc.?

Regulatory filings show Jeff Bezos owns almost 79 million shares (AMZN) of the company, worth about $130 billion as of Thursday.

If MacKenzie takes a chunk in a settlement -- or either party needs to liquidate their assets to meet divorce expenses -- those could become part of the company’s freely traded stock. In turn, that could boost the company’s weighting in indexes including the S&P 500 -- sending tracker funds on a small Amazon shopping spree.

“From the perspective of the index, you’d need to a sell a little of everything else and buy some Amazon,” said David Dziekanski, a portfolio manager at Toroso Investments. “The equity markets will absorb any Amazon additional shares without much impact on price.”

It’s a speculative yet pertinent question, given that about $3.4 trillion is pegged to the S&P 500, and another $6.5 trillion uses the gauge as a benchmark. That’s put the wonky methodology governing indexes like the S&P 500 center stage.

The gauge uses a company’s float, rather than the total number of shares outstanding, to determine its weight in the index, and it calculates the float by excluding shares owned by the company’s officers and directors as well as individuals owning 5 percent or more of a company.

Amazon’s allocation is therefore adjusted down to exclude Jeff Bezos’s 16 percent stake. If MacKenzie Bezos walks away from the marriage with 24 million of those shares -- just under S&P’s 5 percent threshold -- Amazon’s float could grow, lifting the company’s slice of the index and potentially generating an $6 billion reshuffling of investments from index trackers needing to bolster their positions.

But S&P methodology also excludes shares owned by “related individuals” of company officers and directors from its float calculation.

The index provider declined to comment on whether that category would include ex-spouses, with a spokeswoman adding that the firm doesn’t typically comment on individual companies.

More simply, the float could grow if either Bezos sells shares to raise cash. Because let’s face it, even Amazon can’t make divorces cheap.