Table schema:
CREATE TABLE table_name_22 (year INTEGER, result VARCHAR, extra VARCHAR, tournament VARCHAR, venue VARCHAR)

Question: What is the average year that anna thompson had an 8th place result in team competition at the world cross country championships in st etienne, france with
SQL: SELECT AVG(year) FROM table_name_22 WHERE tournament = "world cross country championships" AND venue = "st etienne, france" AND extra = "team competition" AND result = "8th"