Twelve months ago, few would have backed a debt-laden used-car sales platform and a building supplies group to be among the standout performers on the US stock market. …In terms of sectors, homebuilders’ success was the one most didn’t see coming. Rising rates were expected to lower house prices but instead they effectively trapped US homeowners reluctant to give up their low 30-year fixed-rate mortgages — something that last happened too long ago for most to remember. The resulting supply shortage squeezed prices to new records and developers couldn’t build fast enough. Even Warren Buffett bought in, but it was a supplier that actually did best. Builders FirstSource rose more than 150%, joining the S&P 500 in December, where its gains rank it in the top five performers for the year. The simplest takeaway is the oldest one: when you first see a gold rush, buy shovels.