Sub-national Estimates, Domains
Number of separate areas (domains) for which separate, equally reliable estimates are wanted affects sample size.
If, say, 5 regional estimates are wanted, then, theoretically, sample should be increased by factor of 5.
Must be careful therefore in producing separate estimates for domains.
Either limit number of domains to avoid large increase in sample size,
Or be prepared to accept domain estimates with much higher sampling errors than national.