How has the custom of sending Christmas cards changed over the past decade?
Does the Post Office deliver fewer items now that everyone has e-mail?
anecdotal evidence would be interesting , too
(I tried a quick google for “Christmas cards +mail volume” but didn’t get any obvious answers)
I used some different keywords and found the relevant articles to your question…
google “christmas cards decline email”
http://www.google.com/search?client=opera&rls=en&q=“christmas+cards”+decline+email
Your question was narrow in scope but I think you can generalize that all handwritten communication via USPS snail mail has declined (wedding invitation RSVP, etc)