characterizing BGP updates (research topic?)

I'm currently looking for data characterizing BGP updates.
This page calls out 'bad' guys:

but I haven't found anything yet which defines the terms or methodologies
used. Is there a key for this page somewhere? Are there similar
data sources for BGP update stats that go into more detail?

I'm personally interested in being able to tell the difference between
new announcements/withdrawals of a prefix to the Internet as a whole
(insufficient redundancy?) vs. changes in best path (next hop). If I can get
my hands on raw BGP update traffic info, I would even consider
taking a stab at doing the analysis myself.

Pointers to data/previous results (as well as comments on why
this is a stupid question) are welcome.

Bill Bogstad