What is the average rank of a nation that had 219,721 in 2012?
CREATE TABLE "top_10_international_visitors_in_vietnam" (
  "rank" real,
  "country" text,
  "2011" real,
  "2012" real,
  "2013_jan_sep_link" text
);
SELECT AVG("rank") FROM "top_10_international_visitors_in_vietnam" WHERE "2012"='219,721';