"Virtual worlds need a standard of measurement and protocol across platforms." (http://www.projectgoodluck.com/blog/2007/02/beyond-second-life-toward-v-economy.php)
Standard Metrics of Use
"Sociologist/statistician Dmitri Williams, among others, is working on a Standard Metrics of Use for population gauge. In a peer-to-peer gesture, Williams has offered up the following categories of measurement as a start:
- Economic activity
- Active users"
"Duration (could also be called "stickyness"): The amount of time the person has been a user of the world, expressed as a population mean with a standard deviation. This would be retroactive time from today, telescoping backwards. The user need not be on every day. Gaps between logins are allowable, with the maximum allowable time gap between logins being 90 days. Use example: "The average user of MegaWorld has a duration of 83 days." The standard deviation of the mean would help explain whether the typical person logged in once and quit or actually hugs the mean.
Intensity: Average hours per day per user. Sure, subject to all kinds of distortions for people who leave accounts logged on for various purposes (selling goods in Lineage 2, e.g.). Nevertheless, pretty useful as an indicator of bandwidth and interest levels and roughly comparable across worlds.
Economic activity A: A binary variable reporting whether the user does or does not pay for access to the virtual world.
Economic activity B: The average amount paid per user per week across the world population.
Multiplicity: Another population mean, an indicator of the number of accounts or avatars maintained by the user. This number would then be used for the previous three to obtain per-character averages. Note that the number could be either more than 1 or a fraction of 1 if the account is shared." (http://terranova.blogs.com/terra_nova/2006/12/standard_metric.html)