How Index Funds Track Illiquid Small Stocks
Summary
The discussion addresses a concern that passive funds may link large amounts of capital to stocks whose daily trading value is small. It distinguishes assets indexed to a stock from the stock’s own market value and explains that an index fund need not hold every constituent in exact proportion to track the benchmark.
Funds can use representative sampling or replace less liquid holdings with similar, more liquid securities. The goal is to keep tracking error low, rather than duplicate all index holdings exactly; the answer says these methods have worked well. It also notes that alternative benchmarks may be easier to track than the Russell 2000. The discussion offers no quantitative evidence about the scale of liquidity risk or the effectiveness of sampling, so it explains tracking mechanics more than it evaluates Burry’s broader concern.
Key ideas
- Index-linked assets do not have to be matched by identical holdings in a fund.
- Funds can sample constituents or substitute liquid, similar securities to reduce trading demands.
- The practical objective is low tracking error rather than exact replication of every index constituent.
- Benchmark design affects how easy an index is to track.
Tags
Full text
# How can more money be indexed to a stock than the stock's actual value? # How can more money be indexed to a stock than the stock's actual value? According to a recent Bloomberg article, Michael Burry of "The Big Short" fame claims that > In the Russell 2000 Index, for instance, the vast majority of stocks are lower volume, lower value-traded stocks. Today I counted 1,049 stocks that traded less than \$5 million in value during the day. That is over half, and almost half of those -- 456 stocks -- traded less than \$1 million during the day. Yet through indexation and passive investing, hundreds of billions are linked to stocks like this. The S&P 500 is no different -- the index contains the world’s largest stocks, but still, 266 stocks -- over half -- traded under \$150 million today. That sounds like a lot, but trillions of dollars in assets globally are indexed to these stocks I fail to see how this demonstrates a problem. Is he suggesting that there is more money indexed to the stocks than the stocks are actually worth? Well that should be quite obvious as one can easily track the real value of the fund based on its reports of which stocks it holds. What is Burry trying to say here ? ## Answer by phdstudent (score 2) https://quant.stackexchange.com/a/47506 Very easily, you don't actually need to hold those stocks as long as you own a portfolio of larger stocks that in the correct proportion can mimic those small stocks. These are called replicating portfolios. Given that those stocks that trade low volumes are also low market cap (highly likely), the tracking error of not holding exactly those is not that big. ## Answer by nbbo2 (score 2) https://quant.stackexchange.com/a/47509 The goal of the index fund is to have a small tracking error (not to replicate the index holdings exactly). They are aware that some stocks are less liquid than others and will use techniques such as sampling (skipping some small stocks entirely) or substitution of more liquid similar stocks to construct their mimicking portfolio. So far these techniques have worked well. Also, indexes easier to track than Russell 2000 have been developed, such as CRSP Total Market Index, so Russell 2000 is not the best example of an index (it is outdated in terms of index methodology, and I don't recommend it).
Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.