My preference is to go by IP Range by "region" and reduce the number of entries. You can look up the IP blocks at http://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xml
These blocks don't go through significant and frequent changes.
AfriNIC Africa, portions of the Indian Ocean
APNIC Portions of Asia, portions of Oceania
ARIN US, Canada, many Caribbean and North Atlantic islands
LACNIC Latin America, portions of the Caribbean
RIPE Europe, the Middle East, Central AsiaOn Ver 5.4-B2012021601: