Why stocks beat gold and bonds?

Investing is often described as the process of laying out money now in the expectation of receiving more money in the future. At Berkshire Hathaway  BRK.A -0.07%  we take a more demanding approach, defining investing as the transfer to others of purchasing power now with the reasoned expectation of receiving more purchasing power —after taxes have been paid on nominal gains — in the future. More succinctly, investing is forgoing consumption now in order to have the ability to consume more at a later date.

From our definition there flows an important corollary: The riskiness of an investment is notmeasured by beta (a Wall Street term encompassing volatility and often used in measuring risk) but rather by the probability — the reasoned probability — of that investment causing its owner a loss of purchasing power over his contemplated holding period. Assets can fluctuate greatly in price and not be risky as long as they are reasonably certain to deliver increased purchasing power over their holding period. And as we will see, a nonfluctuating asset can be laden with risk.

Investment possibilities are both many and varied. There are three major categories, however, and it’s important to understand the characteristics of each. So let’s survey the field.

Investments that are denominated in a given currency include money-market funds, bonds, mortgages, bank deposits, and other instruments. Most of these currency-based investments are thought of as “safe.” In truth they are among the most dangerous of assets. Their beta may be zero, but their risk is huge.

Over the past century these instruments have destroyed the purchasing power of investors in many countries, even as these holders continued to receive timely payments of interest and principal. This ugly result, moreover, will forever recur. Governments determine the ultimate value of money, and systemic forces will sometimes cause them to gravitate to policies that produce inflation. From time to time such policies spin out of control.

Even in the U.S., where the wish for a stable currency is strong, the dollar has fallen a staggering 86% in value since 1965, when I took over management of Berkshire. It takes no less than $7 today to buy what $1 did at that time. Consequently, a tax-free institution would have needed 4.3% interest annually from bond investments over that period to simply maintain its purchasing power. Its managers would have been kidding themselves if they thought of any portion of that interest as “income.”

For taxpaying investors like you and me, the picture has been far worse. During the same 47-year period, continuous rolling of U.S. Treasury bills produced 5.7% annually. That sounds satisfactory. But if an individual investor paid personal income taxes at a rate averaging 25%, this 5.7% return would have yieldednothing in the way of real income. This investor’s visible income tax would have stripped him of 1.4 points of the stated yield, and the invisible inflation tax would have devoured the remaining 4.3 points. It’s noteworthy that the implicit inflation “tax” was more than triple the explicit income tax that our investor probably thought of as his main burden. “In God We Trust” may be imprinted on our currency, but the hand that activates our government’s printing press has been all too human.

High interest rates, of course, can compensate purchasers for the inflation risk they face with currency-based investments — and indeed, rates in the early 1980s did that job nicely. Current rates, however, do not come close to offsetting the purchasing-power risk that investors assume. Right now bonds should come with a warning label.