Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_63864 ( "Year" real, "Population" real, "Five Year % change" text, "Ten Year % change" text, "Rank Among Provinces" real )

### Question ###
What is the highest population for the province having a rank under 5?

### Accurate SQL ###

SELECT MAX("Population") FROM table_63864 WHERE "Rank Among Provinces" < '5'