You're right, I've should have specified the dates I used were when they announced their plans, not completed them.

It all happened so quickly and at such a large scale. When merged (Dec 2015), DowDuPont was the largest chemical company in the world by far. They merge to reorganize their assets, secrets, and liabilities with each other while creating a new public stock for a short amount of time. They broke up in March 2017 into 3, more product-concentrated companies. Dow, DuPont, and Corteva were the result and are still industry leaders today. In hindsight it appears DuPont and Dow split up assets and secrets in a tax-efficient/dodging way. Dow seemed to get the better deal in the end imo.

The Dow/DuPont merger was an odd one. Had to do a case study on it in college, worth the Google search.