what may be gained in mathematical precision is lost by the compounding of uncertainties, particularly about growth, over the term of 34 years: they make any numbers we may calculate with conjectural. It may be more appropriate to derive an empirical estimate of duration, and encapsulate it in a rule of thumb that's reasonable most of the time. Price sensitivity versus duration The price sensitivity of a stock versus duration, often called modified duration, is the percentage change in price in response to a 1% change in the long-term return that the stock is priced to deliver. The modified duration is duration divided by (1 + growth rate). There is some ambiguity in the literature when referring to duration; much of the time modified duration is referred to simply as "duration", and they have similar values, so much confusion results. Convexity The modified duration formula assumes a linear relationship between percent change in return and percent change in price; but because returns compound, it overestimates the actual change in price. This difference is called "convexity". See also Bond duration References Buy-and-Hold For the Duration? Equity securities