Week 24 Day 1: The Lindy Effect: Old Is Stronger Than New

Nassim Taleb popularized the Lindy Effect: for non-perishable things (ideas, technologies, strategies), age is a sign of strength, not weakness. A restaurant that has been open for 30 years is more likely to last another 30 than one that opened last month. Index investing, diversification, and compound interest have been proven for a century. Trust old wisdom over new hype.

The Lindy Effect applied to investing: Index investing: 50 years of evidence (since 1976). Buy-and-hold: 100+ years of evidence. Diversification: 70+ years since Markowitz (1952). Compound interest: 400+ years since it was formalized. Value investing: 90 years since Graham and Dodd (1934). These strategies pass the Lindy test. Now consider what does NOT pass: Crypto: 15 years old. SPACs: hyped in 2020-2021, dead by 2023. NFTs: peaked 2021, collapsed 2022. Leveraged ETFs: designed for day trading, terrible long-term track record. Robo-advisors: useful but only 12 years old. The pattern: most 'revolutionary' investment products are either old ideas repackaged expensively or genuinely new ideas that have not been tested through a full market cycle. Before adopting any new strategy, ask: 'Has this survived a crash, a recession, and a decade of underperformance?' If the answer is no, you are the test subject.

The Lindy Effect, formalized by Mandelbrot (1982) and popularized by Taleb (2012), states that for non-perishable entities, the remaining life expectancy is proportional to the current age. This applies when the hazard function is decreasing over time -- each additional year of survival provides evidence of robustness. The mathematical formulation: if X has survived t years, E[remaining life | survived t] = t * (alpha / (alpha-1)) for a Pareto-distributed survival function with shape parameter alpha > 1. Applied to investment strategies: index investing has survived 50 years of financial innovation, multiple attempts at disruption, and every market crisis -- each survival increases our confidence in its future viability. Conversely, strategies less than 10 years old have not been tested by a full cycle of bull market, bear market, and recovery. Baillie, Bollerslev, and Mikkelsen (1996) showed that financial market regularities (risk premia, mean reversion, momentum) exhibit long memory -- the same patterns persist over centuries, not just decades. This provides independent support for trusting time-tested strategies. The practical filter: before allocating capital to any strategy, verify that it has survived at least two bear markets. If it has not, it is an untested hypothesis, not a proven strategy.