I was trying to bring to mind the slippage that these kinds of funds incur on a regular basis when they need to constantly roll the front month contracts out into the future with longer dated contracts. My opinion is that funds managed in this manner may not really be suitable for someone who wants long term exposure to the underlying commodity.
Now I'm a bit confused. This slippage you speak of sounds much like the reason that index funds trail indexes. A small inefficiency, but significant in long terms. I am not interested in JJG as a long term prospect. I'm only interested because of the price, when that changes, so will my interest.
For example, I am a landlord with 2 rental houses, I may buy more, but not now. Because prices are too high. Rents are also high, but when the next recession hits, rents will fall, but mortgage payments stay the same. So, given current prices, I am looking at other investments.
I want the volatility. That is why I am looking at a low priced commodity, rather than the REIT of the farmland that produces the commodity. Low corn price will drop the return for corn farmers, a bit. So the REIT will drop a bit, maybe. This pretty much negates the opportunity.. As much as I dislike gold as an investment, if it was 400/oz, right now, I would buy gold, not a gold mining stock, or fund.
If there is a better way to do this, I am all ears.