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If the Efficient Market Hypothesis is true, shouldn't it be almost as hard to lose money on the market as it is to gain money? Let's say you had a strategy S that reliably loses money. Shouldn't you be able to define an inverse strategy S', that buys when S sells and sells when S buys, that reliably earns money? For the sake of argument rule out obvious errors like offering to buy a stock for $1 more than its current price.
Hugely important to distinguish between investing and trading here. But the short answer is that it'd be near impossible to lose money systematically without knowing the inverse (more profitable) strategy.
Consider the scenario where a 22-year-old teacher named Warren, who knows nothing about finance, takes 80% of his annual salary and buys random stocks with the intent to hold until retirement age (reinvesting all dividends). It would be extraordinarily fluky for him to not make solid returns over the long-run with this approach, let alone break even or ... (read more)