Table schema:
CREATE TABLE table_19948664_1 (countries_sampled VARCHAR, ranking_la__2_ VARCHAR, world_ranking__1_ VARCHAR)

Question: How many countries were sampled for the index in 2nd place in the LA ranking and 23rd in the world ranking?
SQL: SELECT countries_sampled FROM table_19948664_1 WHERE ranking_la__2_ = "2nd" AND world_ranking__1_ = "23rd"