As far as I know, all Japanese have their family names in Kanji.  However,
for first names, both Hiragana and Katakana are used too.

Even so, most Japanese have Kanji first names, while some women (about
5% according to my parents) have Hiragana first names.  Foreign names are
almost always in Katakana.

What I'm asking here is this: How popular are first names given in
Hiragana and Katakana for boys in Japan?

Does anyone know?
Thanks.

-kira