An entire generation of investors has been misled about interest rates: where they come from, what they mean, how they're determined.

Lots of this confusion has to do with the role of central banks. Many think central banks, like the Fed, control all interest rates. This isn't true. They can only control short-term rates. It's true these can have an impact on other rates, but it doesn't mean they control the entire yield curve.

Ultimately, an interest rate is simply the cost of transferring consumption over time. If someone wants to save (spend less than they earn today) in order to consume more in the future, they must find someone else who wants to spend more today than they earn, and then repay in the future.

Savers (lenders) want to be compensated by maintaining - or improving - their future purchasing power, which means they need payment for three things: inflation, credit risk, and taxes.

Lenders deserve compensation for inflation. Credit risk – the chance a loan will not be repaid – is also part of any interest rate. And, of course, those who earn interest owe taxes on that income. After taxes, investors deserve a positive return. In other words, interest rates that naturally occur in a competitive marketplace should include these three factors.

So, why haven't they? In July 2012, the 10-year Treasury yield averaged just 1.53%. But since then, the consumer price index alone is up 1.5% per year. An investor who paid a tax rate of 25% would owe roughly 0.375% of the 1.53% yield in taxes. In other words, after inflation and taxes (and without even thinking about credit risk, which on a Treasury is essentially nil), someone who bought a 10-year bond in July 2012 has lost 0.35% of purchasing power each year, in addition to capital losses as bond prices have declined.

Something is off. The bond market has not been compensating investors for saving, it has been punishing them.