To avoid investing in a business that’s in decline, there’s a few financial metrics that can provide early indications of aging. When we see a declining return on capital employed (ROCE) in conjunction with a declining base of capital employed, that’s often how a mature business shows signs of aging. This combination can tell you that not only is the company investing less, it’s earning less on what it does invest. And from a first read, things don’t look too good at Wabash National (NYSE:WNC), so let’s see why. What Is Return On Capital Employed (ROCE)? Just to clarify if you’re unsure, ROCE is a metric for evaluating how much…