How many countries spent at least $51.0 billion in international tourism in 2012?
CREATE TABLE "international_tourism_expenditure" (
  "rank_2012" real,
  "country" text,
  "unwto_region" text,
  "international_tourism_expenditure_2011" text,
  "international_tourism_expenditure_2012" text,
  "pct_change" text
);
SELECT MAX("rank_2012") FROM "international_tourism_expenditure" WHERE "international_tourism_expenditure_2011"='$51.0 billion';