What is the total number in 2006, which has an official foundation of municipality of 1918?
CREATE TABLE "cities_over_1_000_000_population" (
  "rank" real,
  "city" text,
  "province" text,
  "date_of_official_foundation_of_municipality" real,
  "2006" real,
  "1996" real,
  "1986" real,
  "1976" real,
  "1966" real,
  "1956" real
);
SELECT COUNT("2006") FROM "cities_over_1_000_000_population" WHERE "date_of_official_foundation_of_municipality"=1918;