The COW and G&W state system lists generally have high overlap, but there are differences in states start and end dates, and also some differences in which numeric code is used for a particular states. Some notable code differences for post-WW2 states to look out for when trying to merge datasets with/from COW to G&W coding are:
| Case | G&W | COW |
|---|---|---|
| Germany after 1990 unification | continue 260 | 255 |
| Yemen after 1990 unification | continue 678 | 679 |
| Serbia after 2006 dissolution of Serbia & Montenegro | 340 | continue 345 |
| Kiribati | 970 | 946 |
| Nauru | 971 | 970 |
| Tuvalu | 973 | 947 |
| Tonga | 972 | 955 |