Portfolio duration
The weighted average duration of the issues held, where the weight is each position's share of market value.
Formula
Weights are taken by market value of the positions, not by the number of bonds: a large position in a short bond pulls the result harder than a small one in a long bond.
How to read the number
A single number answering how far the portfolio falls when the whole curve shifts.
When the metric lies
Also known as: average portfolio duration