1. A computer-implemented method, comprising: determining web-based market metric values for a plurality of regions, the web-based market metric values measuring the performance of advertising on the Web in the plurality of regions by an advertising service, wherein the web-based market metric values are selected from a group consisting of advertisement clicks, advertisement click-through rates, advertisement conversions, advertisement conversion rates, advertisement quality, advertisement costs per action, advertisement revenue rates, advertisement revenue per action, and computer web access penetration; clustering the regions into market clusters based at least in part on the similarity of web-based market metric values for each cluster; identifying a cluster transition for a region, the cluster transition defining a transition of the region from a first cluster to a second cluster; and implementing, by a computer system, market-specific changes for the region based on the particular identified cluster transition for the region and the web-based market metric values for the first cluster and the second cluster, wherein the market-specific changes are selected from a group consisting of adjustments to quality factors for serving advertisements, adjustments to bidding requirements for serving advertisements, adjustments to a pricing model for bidding on advertisements, adjustments to promotion of location of advertisements on Web pages, adjustments to keyword expansion for submitted search queries, offering an initial internet access subsidy, and adjustments to the initial internet access subsidy.