Week 19 Day 2: Index Funds: The Greatest Financial Innovation

An index fund buys every stock in an index (like the S&P 500) in proportion to each stock's size. No stock picking. No market timing. Just own the whole market at the lowest possible cost. Vanguard's S&P 500 fund (VOO) charges 0.03% -- that is $3 per year on a $10,000 investment. Active funds charge $50-100+ for worse performance.

The index fund revolution in numbers: Vanguard now manages over $8.6 trillion. BlackRock's iShares manages over $3.5 trillion. Together, Vanguard, BlackRock, and State Street manage more than $22 trillion, primarily in index funds. Index funds now represent over 50% of all U.S. equity fund assets, surpassing active management for the first time in 2019. Why index funds work: (1) Lowest possible costs (0.03% vs. 0.70% average active). (2) Maximum diversification (own hundreds or thousands of stocks). (3) Tax efficiency (low turnover means few capital gains distributions). (4) Simplicity (no manager to evaluate, no style drift). (5) Guaranteed market return (you will never dramatically underperform). The core three-fund portfolio: VTI (U.S. Total Stock Market, 0.03%), VXUS (International Stock, 0.07%), BND (U.S. Total Bond Market, 0.03%). These three funds give you exposure to the entire global investment universe for an average cost of about 0.05%. Warren Buffett has instructed his estate trustee to invest 90% in an S&P 500 index fund and 10% in short-term Treasuries. If it is good enough for the greatest investor in history, it is good enough for you.

The growth of index investing has sparked debate about market efficiency and systemic risk. Critics raise several concerns: (1) Price discovery: if everyone indexes, who sets prices? Stambaugh (2014) argued that even small amounts of active management are sufficient for price discovery. As of 2024, active trading still represents approximately 80% of daily volume. (2) Common ownership: the Big Three (Vanguard, BlackRock, State Street) are now the largest shareholders in virtually every S&P 500 company, raising antitrust concerns. Azar, Schmalz, and Tecu (2018) found evidence that common ownership by index funds leads to higher prices in the airline industry, though this finding is contested. (3) Concentration risk: as index funds grow, they must buy more of the largest stocks (cap-weighted indices), potentially creating a momentum feedback loop. However, Israeli, Lee, and Sridharan (2017) found no evidence that indexing has impaired market efficiency as measured by earnings surprise reactions, analyst forecast accuracy, or bid-ask spreads. (4) Governance: how do passive shareholders vote? Vanguard and BlackRock have developed internal stewardship teams (hundreds of people) that engage with companies on governance issues. The empirical evidence to date suggests index investing has not degraded market functioning, but the question deserves continued monitoring as passive share grows.