As a bellwether indicator for economic health, the transportation sector of the equity market tends to foresee a downturn coming. When the transports start under performing the market as a whole, it is seen as a negative. This is likely because the shipping of intermediate and finished goods has dropped off and there is less overall demand being seen on the front lines of business.
As you can easily see, since the US election transports are hurting.They are under performing the S&P 500 by over 15%. This is surely not a good sign. Keeping an eye on this divergence would be wise.
Source: WSJ Daily Shot 11.13.17