Both the dielectric and skin-effect loss mechanisms tend
to shrink the fastest moving portions of a digital signal.
If you want to know precisely how much shrinkage to
expect, get a copy of my new book, High-Speed Signal Propagation, which
contains all the equations you need to produce these time-domain
displays of skin-effect and dielectric-effect loss mechanisms.
For more
details, see Johnson & Graham,
High-Speed Signal Propagation
Prentice-Hall 2003