> large expansion of corn acreage

Corn acres have expanded, but the same is also true of other crops. Given corn's role in the crop rotation, it stands to reason that when other crops expand, corn comes with it. There are a lot more mouths to feed nowadays. The world's population has grown by approximately 30% since the last change in ethanol policy.

> that corresponds to ethanol policy.

The ethanol subsidy in the last policy change ended in 2012, yet, as you point out, corn acres have continued to expand, which seems contrary to what you are trying to suggest. What specific correspondence are you finding?