Amazon and e-commerce have made shopping a whole lot easier (and made us a whole lot lazier), but research shows that Costco, Sam’s and other warehouse clubs have had a greater effect on retail in the last 15 to 20 years than we might think. In a new paper from the National Bureau of Economic Research, the University of Chicago’s Ali Hortacsu and Chad Syverson compared the relative size and growth trajectories of warehouse clubs and e-commerce sites and found that while e-commerce sprouted 10-fold from 1992 to 2013 ($35B to $348B), warehouses grew even more, a 10.5-fold increase ($40B to $420B). These findings confirm that, despite analysts' concerns, brick-and-mortar isn’t fading into obscurity (in fact, some websites have gone that route). But this study doesn’t mean that retailers are going to be adopting warehouse club models over improved digital capabilities. So while warehouse still may the top dog, we’re quickly reaching a point where the balance may tip in e-commerce’s favor. [WaPo]