public static String getPopulation(String date, String state, String gender) 
  {
    DB db = _mongo.getDB(DATABASE_NAME);
    DBCollection coll = db.getCollection(COLLECTION_POPULATION);
    
    BasicDBObject query = new BasicDBObject();
    query.put("year", "" + getYear(date));
    
    DBCursor cur = coll.find(query);

    DBObject doc = null;
    if (cur.hasNext()) {
      doc = cur.next();
      if (gender == null) gender = GENDER_ALL;
      return getValue(doc, state, gender);
    }
    
    return "";
  }