Top U.S. ISPs by Subscriber:
How We Count

On this page, we show how we calculate the total U.S. ISP market and individual ISPs' market share.

by Alex Goldman ISP-Planet Managing Editor [June 15, 2006]

This table shows subscriber growth rates at the ISPs we watch:

Unique subscribers
In order to calculate the number of subscribers in the rest of the U.S., we have to take the number of subscriber in the U.S., provided by Jupiter Research, and subtract the number of unique subscribers in the ISPs in our list.

Jupiter Research estimates that there were 83.1 million residential subscribers in the U.S on March 31, 2006.

The ISPs in our rankings account for approximately 60,783,000 unique subscribers. We try not to count any subscriber twice. For example, a subscriber to EarthLink DSL may also be counted in Covad's DSL numbers and in the ILEC's DSL numbers as well. We therefore do not count EarthLink and Covad broadband towards our total.

We assume that 20 percent of AOL's subscriber base obtains access through another ISP, either as BYOA, or in a more traditional broadband arrangement. As AOL and Road Runner work together more and more, we expect the subscriber bases to overlap more than they do today, and hope that AOL, which is very good about disclosure, will reveal the extent of the subscriber overlap.

This leaves us with the following unique subscriber numbers:

Here's how we calculate the number of subscribers of the rest of the ISPs in the U.S. We substract the number of unique subscribers, 60,783,000, from the 83.1 million total individual subscribers. That gives us 22,317,000, or approximately 22.3 million subscribers for the rest of the ISPs in the U.S., which is 24.1 percent of the market.

Market share calculation
So how many subscribers were not unique subscribers? The total subscribership of our ISPs is 70,331,400. Of this, we believe that 60,783,000 are unique subscribers. The remainder, 9,548,400, we believe appear in the numbers of more than one ISP on our list.

In order to calculate market share, we add the remainder, 9,548,400, to the Jupiter Research subscriber total, 83,100,000, to get 92,648,400, which we use to determine the market share of each ISP. This is the total number of unique subscribers in the United States plus the number of double-counted subscribers in the ISPs listed in our table.

Here is a sample market share calcluation: AOL's apparent ISP total (including non-unique subscribers) is 18,640,000. We divide 18,640,000 by 92,648,400 to obtain the market share percentage shown on our table, 20.1 percent.

Transparency
In building subscriber rankings, we are constantly frustrated by the quality of the data we are forced to work with. We have, in contrast, endeavored to make our sources plain and our calculations obvious. We welcome feedback.

Also note that almost all companies on the list are public companies. We would like to list all providers, including non-facilities based companies, but most ISPs are privately held and do not disclose subscriber numbers at all (certainly not on a quarterly basis).

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Online Resources:
	Jupiter Research: Broadband
	Subscriber Ranking History
	Subscriber Value by Category