Duration

Duration is a measure of the weighted average time until a Bond's cash flows (coupon payments and principal repayment) are received. More practically, it indicates how much a bond's price will change for a given change in interest rates. A bond with 7-year duration will see approximately 7% price change for every 1% change in yields.

There are two common types: Macaulay Duration (the weighted average time to receive cash flows, measured in years) and Modified Duration (which adjusts Macaulay Duration for the yield, directly measuring price sensitivity). For most practical purposes in Indian bond investing, modified duration is the relevant metric.

In the Indian fixed-income market, duration drives investment strategy. When you expect the RBI to cut interest rates (easing cycle), you want higher duration bonds — a 10% bond with 15-year duration will rise approximately 15% in price if yields drop 1%. When you expect rate hikes (tightening cycle), you want short-duration instruments to minimise price losses. In 2023, many institutional investors loaded up on long-duration G-Secs anticipating rate cuts, profiting when the 10-year yield fell from 7.5% to 7.0%.

For mutual fund investors, duration is the key differentiator between debt fund categories. Liquid funds (duration: 30-90 days) have near-zero price sensitivity to rates. Short-duration funds (1-3 year duration) have moderate sensitivity. Gilt funds (5-12 year duration) are highly sensitive to rate movements. SEBI categorises debt funds partly by duration, making it easier for investors to choose: overnight funds (1 day), ultra-short (3-6 months), low duration (6-12 months), short duration (1-3 years), medium duration (3-4 years), and long duration (7+ years).

A key concept is "duration matching" — aligning your investment duration with your goal horizon. If you need money in 3 years, invest in a fund with approximately 3-year duration. This ensures that even if rates move adversely, the reinvestment effect offsets the price effect by your target date. Indian financial advisors increasingly use this approach for goal-based fixed-income allocation, matching PPF (15-year lock-in) and long-duration bonds to retirement goals, and short-duration funds to near-term goals like car purchases or vacations.