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.