def self.update!
    # New years' "master" files may or may not include previous years' orgs. Bah.
    %w(80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 12).each do |year|
      prev_mtime = File.mtime(File.join(FILES_DIR, "cm#{year}.zip")) rescue nil
      # wget -N preserves the ftp server's date