CREATE TABLE table_name_51 (change___percentage_ INTEGER, land_area__km²_ VARCHAR(255), population_density__per_km²_ VARCHAR(255))
What is the average change to have a land area of 546.74 and a population density greater than 0.5?
    
SQL: SELECT AVG(change___percentage_) FROM table_name_51 WHERE land_area__km²_ = 546.74 AND population_density__per_km²_ > 0.5