What significant disadvantage do open-end mutual funds have compared to ETFs?

Open-end mutual funds are subject to tax inefficiency primarily due to the way they are structured in terms of transactions. When an investor redeems shares from an open-end mutual fund, the manager may need to sell underlying securities to meet the redemption request, which can trigger capital gains that are then distributed to all shareholders. This means that all investors in the fund could end up with a tax liability regardless of their individual investment strategies or how long they’ve held their shares.

In contrast, exchange-traded funds (ETFs) typically allow investors to buy and sell shares on an exchange, providing more tax-efficient structures. They make use of "in-kind" transactions, allowing for the transfer of securities rather than cash when new shares are created or old shares are redeemed, which can help minimize capital gains distributions. This significant tax efficiency is one key reason why many investors prefer ETFs over open-end mutual funds.

Other choices, while relevant to investment vehicles, do not encapsulate the major disadvantage of open-end mutual funds in terms of tax implications.