cw

cw is a fast replacement for wc that counts word, line, character and byte counts. Counts of multiple files may be accelerated with the --threads option.

'xargs <files cw --threads=12' ran
  2.01 ± 0.03 times faster than 'xargs <files cw --threads=4'
 11.55 ± 0.15 times faster than 'xargs <files wc'