Table schema:
CREATE TABLE table_name_88 (area__sq_mi_ INTEGER, administrative_division VARCHAR, national_share___percentage_ VARCHAR)

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 table_name_88 WHERE administrative_division = "hunan" AND national_share___percentage_ < 2.19