The American chemicals market has seen a remarkable turnaround in recent years.

One reason for this reveral of fortune is a recent wave of what Jason McLinn, a partner with Bain & Company, calls "portfolio reshaping". Commodity chemicals, which are bulk produced, and specialty chemicals do not have much to do with each other, he says, but chemicals firms seeking growth in sluggish markets like America typically developed both. Now, under pressure from investors, bosses are spinning off non-essential businesses and bulking up in their areas of strengths.