  The fraction of white dwarfs found in wide binaries is estimated by cross
referencing a catalogue of wide binaries with catalogues photometrically
determined white-dwarf candidates and spectroscopically confirmed white dwarf
stars. The wide-binary fraction of white dwarfs with hydrogen-dominated
atmospheres is about 5%, but the fraction of white dwarfs with helium or
carbon-dominated atmospheres is significantly larger. Using spectroscopic
classifications, the binary fraction of DA white dwarfs is determined to be
$0.063\pm0.002$ and for non-DA white dwarfs is larger at $0.080\pm0.004$.
