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_53636 ( "City" text, "1970" real, "1980" real, "1990" real, "2000" real, "2010 est." real )

### Question ###
Of 2010 est. with less than 171,750 and 2000 less than 131,714, what is the 1970 population average?

### Accurate SQL ###

SELECT AVG("1970") FROM table_53636 WHERE "2010 est." = '171,750' AND "2000" < '131,714'