On the topic of duration of a portfolio, when to add and deduct liability duration

in a leveraged portfolio, you have Da*A = Dl*L + De *E

but i think in calculating your position in equity you deduct short position duration? Is there a summary of when is the liability duration added and when it is deducted?


Do it like this …

Duration of Portfolio = (Duration of Assets x Assets) - (Duration of Liabilities x Liabilities) / Equity

Equity = Assets - Liabilities

Liabilities = Amount borrowed (amount of leverage)