emailmarketing McKinsey: It’s a postholiday tradition up there with returning unwanted gifts and vowing to exercise more: spending a few hours cleaning out your e-mail inbox. If you’re wondering why marketers seem intent on e-mailing you more and more, there’s a simple explanation: it works. E-mail remains a significantly more effective way to acquire customers than social media—nearly 40 times that of Facebook and Twitter combined. That’s because 91 percent of all US consumers still use e-mail daily, and the rate at which e-mails prompt purchases is not only estimated to be at least three times that of social media, but the average order value is also 17 percent higher.