That is not a typo. According to the American Stock Exchange (AMEX), net assets in the world's largest ETF grew from $70.9 billion on September 14 to $91.6 billion on September 21. 

To put that in perspective, there are only two other ETFs in the world that have more than $20 billion in assets total: the iShares MSCI EAFE (EFA) ($47.6 billion) and iShares MSCI Emerging Markets ($20.9 billion).

SPY now makes up 16% of total U.S. ETF industry assets, and is larger than the smallest 491 ETFs combined. With an expense ratio of 10 basis points, it grosses a hefty $91.6 million a year in fees.

It is also the largest mutual fund in the world if you look at share classes independently ... larger than the Vanguard 500 Investor Shares and the American Funds Growth Fund of America A-Shares.

Sometimes we forget that this is a top-heavy industry, and that some of the biggest, most interesting and most important developments take place with some of the oldest, most traditional and most-often-overlooked funds.