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Contango, Futures ETF Roll Yield, and Constant-Maturity Exposure

Article Quant Q&A · Author: qwer
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Summary

The question examines why futures-based exchange-traded products can decline over time in contango, using crude-oil and volatility products as examples. It distinguishes losses attributed to selling an expiring nearby contract and buying a more expensive deferred contract from losses that arise as a held contract moves along an unchanged upward-sloping futures curve toward expiry. The writer questions whether a constant-maturity index’s changing weights between nearby maturities make the roll itself economically meaningful.

The discussion also contrasts maintaining a fixed number of contracts with targeting a constant time to maturity, and asks how index funds schedule rebalancing and handle discrete contract sizes. It offers no definitive resolution or empirical test: these are open conceptual questions prompted by a secondary article’s toy example. Actual outcomes depend on the index’s exposure target, rebalancing rules, futures-price changes, and implementation costs; contango alone does not specify realized fund returns.

Key ideas

  • Futures ETFs may face losses in contango, but the source questions how to attribute those losses to rolling versus futures-price convergence.
  • A constant-maturity exposure typically changes the portfolio weights across contract months over time.
  • Rolling a fixed number of contracts differs from rebalancing to maintain a target maturity or exposure.
  • Index rules determine when and how futures positions are shifted between maturities.
  • The document raises implementation questions but does not supply a conclusive analysis or test.

Tags

FuturesVolatilityCommoditiesCarryDerivatives pricing
Full text
# Is there really a negative roll yield for futures in contango?


# Is there really a negative roll yield for futures in contango?












I am trying to wrap my head around how ETFs that track futures work (whether its USO tracking WTI futures or VXX tracking VIX futures).

I have read online about how for normal contango environments, ETFs tracking those futures will lose value over time because of the roll yield (when the nearby futures expires, the fund needs to buy the next month future in order to maintain same exposure, but for normal contango environments, it means that price is generally higher). ETF Negative Roll Yield

However, the article below seems to demonstrate that for the VIX at least, that is not the case. https://sixfigureinvesting.com/2016/09/the-cost-of-contango-its-not-the-daily-roll/

In his post, he attributes the loss of the VXX ETF over time not to the actual rolling of the index, but due to the fact that as time goes closer to maturity, the contract will slide down that contago curve, and that movement is the thing that drives price declines.

My questions:

- In his toy example, if he keeps the term structure the same from day to day, the roll cost doesnt factor into the overall value of his Nov/Dec aggregate because the number of contract changes but the value does not. This seems not right? If the ETF is targeting some constant time to maturity exposure, because the overall value split by month is now 84%/16% vs 88%/12%, the value weighted time to maturity will have changed from day to day. In my mind, dont most funds target this constant maturity? Like if I want constant 30 day exposure. Starting from day 0, I buy nearby expiring 30 days from today. Day 1, I now need to shift 1/30 in value from the nearby contract to the 2nd nearby (which say is now 59 days to expiry), so that my value weighted time to maturity remains at 30 days?

- If say I were to be long SPY futures, if I simply wanted to roll my exposure from one contract to the next as they expired, my wanting to buy 1 contract each time seems like it will incur a roll cost because I want a constant 1 contract exposure

- If my understanding of ETFs targeting specific constant maturity is correct, how and when do these ETFs decide to roll their exposures? Ie do they do it at end of day? Also I would imagine, it may be difficult to maintain exact constant maturity because you cant have fractional future contracts, so what error tolerance do they allow?

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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.