A lot of people throw around terms and assumptions without questioning them deeply. One of the most common assumptions is that stocks beat bonds (and beat the heck out of cash) “over the long haul”.
The basis in fact for this assumption is the long term equity records in the USA, the UK and Canada. These markets, over the long haul, have provided returns beyond bonds and cash.
Why only these markets? Because the rest of the markets (Germany, Japan, China, etc…) had some sort of cataclysmic event (World War, hyperinflation, or takeover by non-capitalist regimes) that make comparisons “over the long haul” useless. Even in these markets it is hard to see how wealth could have been preserved; cash (currency) was debased and debts were reneged upon, so all bets were off.
One key element of the “returns beat bonds and cash” is the assumption that you stay the course through horrendous market periods, hold on to equities, and then ride the upward ticks. If you act as many people do and sell when the market gets difficult, you are apt to be out of the market when it shoots upwards. Some of these bear markets are very lengthy and you have to have nerves of steel to ride them out.