MSCI, which owns the Global Industry Classification Standard (GICS), has proposed a set of changes to the way it classifies companies according to sectors, reports Barron’s. The changes could affect the nearly $200 billion assets currently in sector-focused index funds, as well as billions in actively managed funds that use the GICS.

For example, Visa, Mastercard and PayPal could move to the financial sector, while ADP and Fidelity National Information Services would shift over to industrials. The market value of the S&P 500’s tech sector could shrink and become even more concentrated than it already is, with Apple and Microsoft accounting for 43% of it. Meanwhile, the share of bank stocks would shrink in the financial sector, the article contends.

If these changes are implemented, the makeup of some sector-focused ETFs that use the GICS to track indexes could alter significantly, including Vanguard IT ($53 billion), Technology Select Sector SPDR ($47 billion) and Fidelity MSCI IT ($7 billion), and their sister funds.

Fund companies don’t have to notify their investors of any alterations in the indexes, so analysts advise checking regularly on your ETFs to make sure they’re still in alignment with what you originally invested in. And, the changes would likely influence the stock-picking decisions of fund managers, and have a greater impact over time, the article concludes.