Trucking goods over land will spread a lot more covid than shipping over sea (with seamen no longer allowed to leave ship). That is the big factor I reckon. So

Trucking goods over land will spread a lot more covid than shipping over sea (with seamen no longer allowed to leave ship). That is the big factor I reckon. So islands will ship everything already, whereas most land-countries move a lot of goods with trucking, and spread the disease that way, even when land-borders are closed. International travel can be closed off with little repercussion.