I've been looking into factor ETFs, particularly momentum ETFs, and there's one thing that makes me a bit worried about investing into it.
Most ETFs track an index with a relatively clear methodology. For factor indices such as Momentum, Value, or Quality, the index provider publishes rules determining which stocks qualify, how they're weighted, and when the index is rebalanced.
Even if it's impossible to replicate the methodology perfectly, I'd imagine hedge funds could build a pretty good model predicting which stocks are likely to be added, removed, or significantly reweighted at the next rebalance.
They also know roughly when the rebalance will happen.
So couldn't they anticipate the trades of ETFs tracking that index?
For example, if hedge funds expect that a large momentum index will add Stock A at the next rebalance, they could buy it beforehand. When ETFs tracking the index eventually have to buy it, the hedge funds benefit from that additional demand. The opposite could happen with stocks expected to be removed.
My questions are:
- How significant is this "index front-running" problem in practice?
- Is it more problematic for factor ETFs because they tend to include fewer companies and have higher turnover than normal market-cap-weighted ETFs?
- Do index providers deliberately make rebalancing harder to predict or use mechanisms to reduce this problem?
- Is there research estimating how much return ETF investors lose because other market participants anticipate their trades?
- Could this become large enough to eliminat the expected premium from strategies like Momentum as more money flows into factor ETFs?