Global Outreach: Why Join SIOR Why Join SIOR Why should you join SIOR? 1. Access to American clients of SIOR's seeking to lease and/or purchase space outside of the U.S. 2. Access to QUALIFIED brokers in the U.S. to assist your clients. 3. Access to SIOR brokers with market expertise in 135 U.S. markets--many of which are not covered by the larger brokerage firms. SIOR Membership Benefits International Requirements Application information and request form