It’s time for our monthly look at how the long-only commodity ETFs are performing versus simply holding the December futures contract and rolling annually.

Crude oil and natural gas both climbed higher in July, but the real story of the month was in the grain markets. Corn shot higher as crop outlooks worsened, and the weather forecast brought little relief. ETF underperformance against the December futures contract narrowed for crude oil and natural gas, but nearly doubled for corn.

Futures trading is complicated, presents a risk of loss, and isn’t for everyone – especially since past market performance doesn’t necessarily indicate future results – but given the numbers, we’re left scratching our heads. Ultimately, we prefer a commodities investment strategy that can benefit from both rising and falling prices (like managed futures). But if you’re going to adopt a long-only strategy… we’ve yet to receive a good answer to the question: why invest in an ETF when you can just roll December futures contracts annually?

Read ‘em and weep: