Cotton

With cotton going limit up so often the ETF that tracks it (BAL) is now actually trading at a premium. 

Might be an interesting idea to for a mean-reversion trade except for the fact that right now you can't buy cotton futures or short BAL.

At first I thought it might be people buying the ETF under the impression that the fund was able buy cotton in an institutional way that retail investors couldn't (swap, creating synthetic futures with options, etc..). 

But a quick look at the prospectus shows that: (sorry for any typos, Dow Jones has silly PDF protection that won't allow me to just copy a paragraph out of the prospectus)

"It is composed of the futures contract on cotton that is included or eligible to be included in the Commodity Index and is intended to reflect the returns that are potentially available through (1) an unleveraged investment in that contract plus (2) the rate of interest that could be earned on cash collateral invested in specific Treasury Bills."

So pretty vanilla stuff. Meaning that mostly likely people buying this ETF thinking they are outsmarting future price limits might be suffering some sub-par returns.