Taco Bell and McDonald’s aren’t the only companies chasing the dollar menu audience. The major financial institutions are in a price war, cutting their ETF expense ratios in a back-and-forth which has led to the steepest decline in fees since the online brokerage was invented during the first dot-com boom.

These are the three forces driving the ETF price war:

1. The Walmart Effect

The three largest ETF issuers (State Street, BlackRock, and Vanguard,) control a staggering 84% of the $3 Trillion dollar market. Vanguard has used a client-owned corporate structure, paired with massive scale, to cut fees and grow assets for decades. However, it has traditionally focused on core ETF offerings that track indices, rather than sector-oriented products like Cybersecurity ETFs.

Recently, Vanguard has started expanding into more sector-oriented products, like international dividend or country-specific ETFs. These types of investments were previously dominated by smaller funds with higher expense ratios. However, as a recent Bloomberg article revealed, Vanguard’s entry has put downward pressure on smaller issuers’ prices, like Walmart opening up next to a mom-and-pop store.

2. Explosive Asset Growth

In the last three years, ETFs have seen record-high inflows as more investors shy away from high-fee and actively-managed products. Today, ETF assets under management stand at $3 trillion, a 430% increase since 2006, and this growth is only expected to continue. In fact, the market is expected to reach $10 trillion in assets by 2020.

At the same time, mutual funds have seen massive outflows as investors opt-out of their high fees and tax inefficiencies. While the ETF AUM has grown 430% since 2006, mutual fund assets have only grown by about 50%, and are expected to stop growing this year.

The expanding industry has issuers rushing to cut fees in hope of soaking up as much ETF market share as possible during this phase of rapid growth.

3. The Fiduciary Rule

Traditionally, ETF issuers used financial advisors as a sales funnel to retail clients. In this scenario, the financial advisor would develop a relationship with an ETF issuer, say BlackRock, and gain a thorough understanding of the products they offer, their structure, and their purpose in a client’s portfolio. Now, suppose the client asks for exposure to high-yield bonds. Their advisor would be more likely to recommend BlackRock’s $HYG, rather than Vanguard’s $VCLT which they know nothing about.

As a result of the sales funnel, the client often ended up purchasing ETFs from whichever issuer was most familiar to their financial advisor, regardless of the expense ratios. For mutual fund investors, the value chain was even more congested. “Soft dollar” arrangements allowed fund managers to artificially reduce their expense ratios by paying for services with order flow. As a result, many investors were paying hidden, undisclosed fees which ate into their returns.

Luckily for investors, this kickback scheme sparked an outrage that resulted in new regulation nicknamed “the fiduciary rule.” The fiduciary rule requires financial advisors to act in the best interest of their client at all times. In short, the fiduciary rule requires financial advisors to suggest low-fee products, and ETF issuers are dropping their fees in order to keep the advisor sales funnel alive.

Thanks to consumer-friendly regulations, an expanding industry, and the Walmart effect, the ETF price war is saving investors billions of dollars as the fees on their investments continue dropping towards zero.