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_11318462_29 (enrolment VARCHAR, in_competition_since VARCHAR, abbreviation VARCHAR)

### Question ###
What is the enrollment of STM which has been in competition since 1990?

### Accurate SQL ###

SELECT COUNT(enrolment) FROM table_11318462_29 WHERE in_competition_since = 1990 AND abbreviation = "STM"