THE next time you read somewhere that the Internet has 20 or 30 million users, or that 50,000 or 100,000 people in Ireland are on the Net, think twice.
These are guesstimates. While capitalism is hyperventilating about the potential of the Internet, it has been a tough nut for the "spreadsheet jockeys" to crack. After all, it's not like counting letterboxes along a street. Nor does the Net have a central organising body as such, or the equivalent of a set of comprehensive phonebooks.
Whatever wild estimate you're reading - whether four or 40 million it's probably based on multiplying an estimate of the number of computers that act as Internet "hosts" or nodes by the estimated number of users per host.
But this users-per-host figure is almost impossible to measure. For example, several people might share the one Internet account, or one person might have accounts with more than one Internet access provider in which ease we're talking about the far more interesting concept of hosts per user, and how much they actually use the Internet: they might have a totally dormant account. Also notoriously unreliable are surveys sent to postmasters (the busy people who look after your system's email) and the response rate is far too low.
A leading expert on the subject, Professor Donna Hoffman of Vanderbilt University in Nashville, Tennessee, argues: "Current approaches to estimating the size of the Internet are akin to estimating the number of people in the US by sampling the number of buildings, without regard to their function or contents."
Which leaves us with surveys of domain names. Little can be extrapolated from these; they don't determine the exact size of the Internet, where the hosts are located, or how many users they have. But they do give a vague, general idea of the Net's growth rate.
The latest survey by Network Wizards (see table) estimates that the Net - in terms of hosts - doubles every 12-15 months. It also reckons that by last month there were at least 21,464 hosts in Ireland (ones that had the ".ie" country code). This coincides almost exactly with the half-yearly count by RIPE (Reseaux IP Europeens) on July 31st, which found 21,483 hosts. Note that most hosts in Northern Ireland would be among the 580,000 hosts with the ".uk" code.
The survey has more caveats than Liz Taylor's marriage licence, and the researchers stress that "we consider the numbers presented in the domain survey to be fairly good estimates of the minimum size of the Internet. We cannot tell if there are hosts or domains we could not locate".
And so the debate continues. How many people are really on the Net? And more importantly, what are they doing there?