Jeff and MacKenzie Bezos\u2019s 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 of the company, worth about $130 billion as of yesterday. 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\u2019s freely traded stock. In turn, that could boost the company\u2019s weighting in indexes including the S&P 500 - sending tracker funds on a small Amazon shopping spree. \u201cFrom the perspective of the index, you\u2019d need to a sell a little of everything else and buy some Amazon,\u201d said David Dziekanski, a portfolio manager at Toroso Investments. \u201cThe equity markets will absorb any Amazon additional shares without much impact on price.\u201d It\u2019s 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\u2019s put the wonky methodology governing indexes like the S&P 500 center stage. The gauge uses a company\u2019s 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\u2019s officers and directors as well as individuals owning 5 percent or more of a company. Amazon\u2019s allocation is therefore adjusted down to exclude Jeff Bezos\u2019s 16 percent stake. If MacKenzie Bezos walks away from the marriage with 24 million of those shares - just under S&P\u2019s 5 percent threshold - Amazon\u2019s float could grow, lifting the company\u2019s slice of the index and potentially generating an $6 billion reshuffling of investments from index trackers needing to bolster their positions. Read Also| Michael Dell gets $12 billion richer with break from public eye But S&P methodology also excludes shares owned by \u201crelated individuals\u201d 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\u2019t typically comment on individual companies. More simply, the float could grow if either Bezos sells shares to raise cash. Because let\u2019s face it, even Amazon can\u2019t make divorces cheap.