What Could Derail Caterpillar Stock?

Investors holding Caterpillar (CAT) stock are paying 33.9 times earnings, compared with 21.9 for the S&P 500. Sustaining that premium requires durable growth, and a rapidly expanding part of Caterpillar's business is selling into a single type of project. During the company's latest earnings call, a concern was raised about how long those projects will keep arriving. So what exactly is the concern.