During California's gold rush, one well-trodden path to riches was selling pickaxes and other handy tools. Today's digital equivalent might be the providers of warehouse automation to e-commerce giants like Amazon.com Inc, Alibaba Group Holding Ltd and JD.com Inc.
As a result, companies such as Germany's Kion Group AG have won fans among so-called thematic investors, who will take a broad trend like e-commerce and bet on what ancillary industries will profit. To be sure, these kinds of wagers are more intellectually satisfying than, say, just buying an S&P500 index fund. But jumping on a theme doesn't always guarantee a smooth ride.