How do you downsize wires?

[Optimistic Paranoid]

You sure of your factoid?  I thought in any current flow the electrons will try to separate themselves.  It is just that with higher voltages there is more energy to push them as far apart as possible.

 -- Spiff

Google "skin effect".  Every single reference I found specifically mentioned it was ac.

 

[Trebor English]

TV cable in homes is wired with RG59. The center conductor is copper plated steel. Only the copper skin conducts, the steel doesn't matter at high frequencies. The voltage is miniscule. Only the frequency affects the skin effect.