Contrary to intuition, even a fully systematic, rules-based investment strategy benefits from an active ETF structure. This approach avoids third-party index licensing fees and provides crucial flexibility to delay rebalancing during volatile market events, a cumbersome process for index-based funds.

Most of an index's returns come from a tiny fraction of its component stocks (e.g., 7% of the Russell 3000). The goal of indexing isn't just diversification; it's a strategy to ensure you own the unpredictable "tail-event" winners, like the next Amazon, that are nearly impossible to identify in advance.

A truly passive portfolio would own all global financial assets in proportion to their market value. However, this is impossible because many assets, like government-held bonds or restricted foreign stocks, are not available to public investors, making every real-world index fund an active bet.

Market-cap-weighted indexes create a perverse momentum loop. As a stock's price rises, its weight in the index increases, forcing new passive capital to buy more of it at inflated prices. This mechanism is the structural opposite of a value-oriented 'buy low, sell high' discipline.

While Berkshire Hathaway is built for durability, the S&P 500 index possesses a unique long-term advantage: its self-cleansing mechanism. As dominant companies inevitably falter over centuries (e.g., NVIDIA), the index automatically replaces them with the next generation of winners. This constant rejuvenation could make the index a more resilient investment over an extremely long timeframe.

The underperformance of active managers in the last decade wasn't just due to the rise of indexing. The historic run of a few mega-cap tech stocks created a market-cap-weighted index that was statistically almost impossible to beat without owning those specific names, leading to lower active share and alpha dispersion.

Contrary to classic theory, markets may be growing less efficient. This is driven not only by passive indexing but also by a structural shift in active management towards short-term, quantitative strategies that prioritize immediate price movements over long-term fundamental value.

Contrary to the belief that indexing creates market inefficiencies, Michael Mauboussin argues the opposite. Indexing removes the weakest, 'closet indexing' players from the active pool, increasing the average skill level of the remaining competition and making it harder to find an edge.

While indexing made competition tougher, the true headwind for active managers was the unprecedented, concentrated performance of a few tech giants. Not owning them was statistically devastating, while owning them reduced active share, creating a no-win scenario for many funds.