Convinced that visitor volume was the key to attracting investors and advertisers, most business-to-consumer (B2C) Internet start-ups spent heavily on branding, on high-impact public relations, and on innovative techniques such as viral and affiliate marketing. These efforts did boost the growth of start-up e-businesses in the short term, but few of them have been able to convert a solid proportion of surfers into buyers and first-time buyers into repeat ones. And without stickiness, as we all now realize, B2C companies have little chance of surviving.

As long as investor confidence remained high, these difficulties didn’t seem to matter. But now that confidence has plummeted, we have an especial need for a metric that can provide early-stage e-businesses—and investors—with the kind of information that companies in more mature industries get from earnings per share and discounted cash flow and all the other techniques developed over the last century to assess the health of companies. To answer this need, the current issue of The McKinsey Quarterly is publishing, in one of its two cover articles, the fruits of the research that the Firm has conducted, over several years, into predictors of commercial success for the different varieties of e-consumer business.

As...