The average client makes a small number of requests to each server. Arlitt and Williamson [2] report that at least 30% of a server's clients make only one request and never request anything from the same server again. If a client is going to request only one document from a server, prefetching makes no sense. If, however, clients go though a proxy, prefetching documents at the proxy may improve performance significantly, since documents prefetched on behalf of one client may also be used by other clients as well.