Although 22 million U.S. home users of online services are not faithful to any particular portal, Yahoo! is gaining ground in the competition for a loyal user base, according to a survey by International Data Corp. (IDC), a Framingham, Mass.-based market research firm specializing in information technology. Yahoo! has greatest reach for home Web users with 47% of the total home Web population. America Online and Netscape rank second and third, respectively, but their reach numbers are distorted by a default home page visits, meaning users' computers automatically open those portals upon launching a Web browser. "A portal may reach several million discrete visitors, but what is truly important in terms of measuring effectiveness is how many of those people are loyal visitors or members, and how long they stay per visit," says Jill Frankle, IDC program manager for Internet and eCommerce Strategies. "As a result, user loyalty and duration are fast replacing reach as the most accurate method of measuring portal effectiveness." According to the survey, Yahoo! has the most loyal user base. Thirty-six percent of its visitors are loyal visitors. Netscape is a close second, with 34%. "Duration is also an important measurement tool as it ties directly into the effectiveness of a portal's business model," says Frankle. "Heavier users are more likely to generate higher ad or transaction revenue." Yahoo! also leads the pack in terms of duration of both discrete visitors and loyal visitors according to the survey. Its discrete visitors stay for an average of 67 minutes; its loyal visitors stay for 161 minutes. Excite ranks second in both categories. Its discrete visitors stay 45 minutes; its loyal visitors stay 160 minutes.