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_1507423_4 ( avg_finish VARCHAR, avg_start VARCHAR )

### Question ###
What was the average finish when the average start was 18.4?

### Accurate SQL ###

SELECT avg_finish FROM table_1507423_4 WHERE avg_start = "18.4"