Over at the Alexa blog at the tail end of a rambling post about the competition for the #2 spot in their ranking we find the following provocative statement:

…over the last six months the Reach and Pageview numbers for both of these giants has been declining, along with Yahoo, in the Alexa stats. That isn’t to say that their overall users or page views are declining, rather that their percentage of the overall traffic on the Web is shrinking.

Markets condense for lots of reasons. Fast growing markets condense because the rapidly entering new customers lack information to guide thier choices leading them to mimic exisiting market players, i.e. you get strong preferential attachment. That concentration of market share can be quite durable since the winners will then work to lock those customers in. As the market matures knowledge about the vendor/customer relationship increases. Vendors get better at managing lock-in while customers become more knowledgable about how to shop.

The relationships that define an industry’s structure. Market share is a metric of the vendor/buy relationships for a particular class of vendors. Individual relationships can come and go, but they tend toward durable. A particular class of relationships is quite durable; which makes market share something dependable. That stablity allows firms to plan their capital expenditures confidently; i.e. it lowers their risk. From a planning point of view how your industry is consilidating or not is as important as if your industry’s market is growing or shrinking.

So I’m particularly bewildered that Alexa doesn’t track and chart an actual measure of how condensed the traffic is.