I noticed this question, How to determine duration of a common stock whose dividends grow in perpetuity? I am familiar with the concept of duration for bonds, but not for common stock (actually, it is unfamiliar to me for equity-type securities of any sort... other than convertible bonds... maybe).
What are the differences in definition and usage of duration for securities that ARE fixed-income versus those that ARE NOT fixed-income?
A bond has a duration that can be easily calculated. It's the time weighted average of all the payments you'll receive and helpful to understand the effect a change in rates will have on that instrument.
The duration of a stock, on the other hand, is a forced construct to then use in other equations to help calculate, say, the summation of a dividend stream. I can calculate the duration of a bond and come up with an answer that's not up for discussion or dispute. The duration of a stock, on the other hand, isn't such a number. Will J&J last 50 more years? Will Apple? Who knows?
