This document discusses expanding a BNI chapter's referral base by considering the network of contacts and opportunities at different tiers - directly from members, from members' contacts, and from contacts' contacts. It shows how the referral opportunities can be much larger than just the other chapter members alone by accounting for each member's network and each contact's network, concluding that the total referral opportunity is the number of members minus one, multiplied by each member's number of contacts, multiplied again by the number of contacts' contacts.