How2 find out how much is DL via upgrades?

[zeek peters <zp1zp11@gmail.com>]

Q: Is there a command/script that finds out how many gigabytes of
upgrades are done on a monthly basis?

I looked at the general options available for "apt-get show"" and
"apt-cache search", but nothing was obvious about how much was downloaded.

Synaptic does provide a "history"" of all the pckgs (File --> History)
that were upgraded/installed sorted by month. Is it possible to take
this list presented by synaptic and find out how many gigabytes where DL
per month?

I know, I could figure this out by manually looking up at what was downloaded
and tally the result for the month.  But is there a way to do this repetitive task 
via script?

Thanks
Cheers