Table: china_divisions_area
Columns: rank
administrative_division
area_km
area_sq_mi
national_share
comparable_country

Question: What is the average area in square miles for the hunan administrative division with a national share less than 2.19%?
SQL: SELECT AVG("area_sq_mi") FROM china_divisions_area WHERE "administrative_division" = 'hunan' AND "national_share" < 2.19