CREATE TABLE table_19948664_1 (countries_sampled INT, index__year_ VARCHAR)

How many countries were sampled for the Prosperity Index (2008)?
SELECT MAX(countries_sampled) FROM table_19948664_1 WHERE index__year_ = "Prosperity Index (2008)"
SELECT MAX("countries_sampled") FROM "table_19948664_1" WHERE "Prosperity Index (2008)" = "index__year_"