节选自intelligent investor by benjamin graham

We think it would be reasonable for an investor at this point to base his thinking and decisions on a probable (far from certain)rate of future inflation of, say, 3% per annum. (This would compare with an annual rate of about 21⁄2% for the entire period 1915–1970.)1
What would be the implications of such an advance? It would eat up, in higher living costs, about one-half the income now
obtainable on good medium-term tax-free bonds (or our assumed after-tax equivalent from high-grade corporate bonds). This would be a serious shrinkage, but it should not be exaggerated. It would not mean that the true value, or the purchasing power, of the investor’s fortune need be reduced over the years. If he spent half his interest income after taxes he would maintain this buying power intact, even against a 3% annual inflation.

why an annual inflation of 3% will eat up about one-half the income now obtainable on good medium-term tax-free bonds and why the buying power will remain intact if half interest income is spent after taxes