There is a tendency to think of mutual funds in binary terms: either actively managed or passive index funds. In reality, it’s a spectrum. Some active funds diverge sharply from their benchmark, making concentrated bets the index barely touches. Others look largely index-like, with only marginal differences.
Both, however, charge active management fees. And disclosures rarely make that distinction obvious. So how do you tell what you are actually paying for?
This is where active share comes in. It puts a number on how differently a fund’s portfolio is constructed relative to its benchmark, helping you spot whether a fund is genuinely active or simply hugging the index.
What active share actually measures
Active share is the percentage of a fund’s portfolio that differs from its benchmark by weight. If a fund mirrors the index exactly, its active share is zero, something no active fund would admit to. At the other extreme, a portfolio with no overlap would have an active share of 100, which is also rare.
Most funds sit somewhere in between.
A fund with 50% active share effectively overlaps half its portfolio with the index, while the rest is allocated either to different stocks or to the same stocks at meaningfully different weights. The higher the number, the more the fund diverges from its benchmark. The lower it is, the more it resembles the index—regardless of how it is marketed.
Consider a fund that holds Stock A as 10% of its portfolio, while that stock has a 40% weight in the benchmark. The absolute difference is 30 percentage points. Calculate this for every stock in the fund and the benchmark, add all the absolute differences, and divide by two (to avoid double counting) to get the active share.
Are you paying active fees for index-like exposure?
An index fund charges for low-cost replication of the market. An active fund charging significantly more is implicitly claiming that its portfolio construction is meaningfully different.
Active share helps you test that claim, before you even look at returns.
If a fund’s active share is low, the obvious question is whether a cheaper index fund tracking the same benchmark would deliver nearly identical exposure. That comparison is worth making.
Does a higher active share mean a better fund?
Not necessarily. A fund can have a high active share and still underperform if its stock selection is poor. Active share tells you how different a fund is, not how good those differences are.
Use it alongside other metrics: long-term performance, consistency of strategy, and expense ratio. It works best as a diagnostic tool, not a verdict.
How to calculate it yourself
Active share is not a standard disclosure in India, but you can calculate it. Fund portfolios are published monthly on websites of asset management companies. Benchmark weights can be approximated using index funds tracking the same benchmark.
Apply the method above. It’s time-consuming—matching 50–100 stocks across portfolios, dealing with naming differences, and accounting for minor tracking errors. Expect to spend at least an hour the first time.
A useful addition to your checklist
As more investors scrutinize expense ratios and past returns, active share offers a missing dimension: whether a fund is actually doing something different. With flows into actively managed equity funds rising, that is a question worth asking.
Nihit Kshatriya is head of investor relations, Capitalmind Mutual Fund