Investors expecting an 'average' 8-10% return each year are often mistaken. Historical data shows returns are not normally distributed; the most common bucket of annual performance is actually 15-20%, followed by 30-35%. Years with average returns are relatively rare.

Calendar year results are arbitrary and can be misleading. A more robust method is to analyze rolling returns, which evaluate performance over fixed periods (e.g., five years) from many different starting points. This method reveals a strategy's true consistency by smoothing out short-term market noise.

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.

Judging investment skill requires observing performance through both bull and bear markets. A fixed period, like 5 or 10 years, can be misleading if it only captures one type of environment, often rewarding mere risk tolerance rather than genuine ability.

Data since 1928 shows the average bull market lasts 2.7 years with a 112% gain, while the average bear market lasts 9.5 months with a 35% loss. This statistical asymmetry heavily favors patient investors who hold through downturns to capture the disproportionately larger and longer recoveries.

The modern market is driven by short-term incentives, with hedge funds and pod shops trading based on quarterly estimates. This creates volatility and mispricing. An investor who can withstand short-term underperformance and maintain a multi-year view can exploit these structural inefficiencies.

Historical analysis of investors like Ben Graham and Charlie Munger reveals a consistent pattern: significant, multi-year periods of lagging the market are not an anomaly but a necessary part of a successful long-term strategy. This reality demands structuring your firm and mindset for inevitable pain.

Timing is more critical than talent. An investor who beat the market by 5% annually from 1960-1980 made less than an investor who underperformed by 5% from 1980-2000. This illustrates how the macro environment and the starting point of an investment journey can have a far greater impact on absolute returns than individual stock-picking skill.

Most investors evaluate performance over a few years, but financial economist Ken French states it's 'crazy' to draw inferences from three, five, or even ten-year periods for an active fund. Shorter timeframes are heavily influenced by randomness and luck, leading to flawed investment decisions.