Investability

Not every well-constructed index can actually be invested in at scale. Investability is the workbook's name for the criterion that checks this. It asks: if a large fund manager tried to buy every stock in this index in its exact weights, could they, without moving the price against themselves?

It sits alongside two other index-design criteria the workbook names in the same breath — liquidity and replicability — as the things a good index provider tests before publishing a benchmark.

The workbook's footnote definition: "The investability of an index is a function of two variables - the liquidity of the underlying constituents and the weight of the securities in the index. The investability of an index determines its investment capacity."

The MSCI India Index is the workbook's worked example of an index built with investability in mind. It has 86 constituents and covers roughly 85% of the market capitalisation of the Indian equity universe. It is reviewed quarterly — in February, May, August and November — and rebalanced, with its large- and mid-cap cut-off points recalculated, during the May and November semi-annual reviews. That review discipline exists partly to keep the index investable: as constituent liquidity and free float shift, stocks that have become too illiquid to buy or sell at scale can be dropped or reweighted.

A passive fund house wants to launch a Rs 800 crore index fund tracking the MSCI India Index and its 86 constituents. For the large, heavily traded names — the top 20 by weight, all constituents of the NIFTY 50 as well — buying the fund's full allocation moves the market price negligibly. That is high investability.

For one smaller constituent near the bottom of the index's weight table, the fund's required purchase would represent several days of the stock's normal traded volume. Executing it in one go would push the price up before the order is filled, and the fund would end up paying more than the index's own valuation implied. This is exactly the liquidity-and-weight interaction the investability criterion is meant to catch — a name can be a legitimate part of the investment opportunity set and still be difficult for a large passive fund to actually hold at its index weight, which is why MSCI's quarterly review exists to re-examine constituents against these tests.

Chapter 12 (Introduction to Indices), section 12.5.9 on MSCI Indices for India, names liquidity, investability and replicability together as the design emphasis behind the MSCI India Index. Expect a recall question naming the three criteria, and a question on the index's quarterly review cycle and May/November rebalancing.

• Investability is not the same as the size of the underlying market. A large, well-known market can still produce an index with poor investability if individual constituents are illiquid or over-weighted relative to their tradeable float.
• Investability and replicability are taught side by side and are easy to swap — investability is about whether you can get the exposure without moving the price; replicability is about whether you can literally hold the same basket the index specifies.
• The MSCI India Index figures — 86 constituents, ~85% market cap coverage, quarterly review, May/November rebalancing — are specific to that index and should not be assumed for NIFTY or Sensex.