Shifting Composition of Core and Periphery

I'm Randy McDonald, a new subscriber to this World Systems list. I'm from
the eastern Canadian province of Prince Edward Island, where I'm in the
middle of my English and Anthropology undergraduate degrees.

I'm familiar with the broad details of the core-periphery world system
pioneered by Wallerstein, and I have pored over the WSN archive so I could
get a broad outline

Looking back at the beginning of the 20th century, you could see a rather
significant difference in the composition of the core states of the emerging
world economy. In the broad world-perspective, Austria-Hungary (or most of
it outside of the impoverished eastern provinces anyway) would seem to have
acquired an enviable central position in European and world economic
patterns. The Southern Cone states -- I mean, Argentina, Chile and Uruguay
-- also had developed-country standards of living, and were major countries
of immigration from Europe and from South American neighbours. Most of
Austria-Hungary has dropped out of the core after the First World War, and
the Southern Cone states have undergone a similar decline, if with a much
smaller incidence of ethnocide. On the other hand, Japan was, at best, only
a peripheral member of the core, while (South) Korea and Taiwan didn't even
count.

I was wondering if there was any theory (or better yet, theorists!)
available that could explain these shifts in the composition of the core
and/or semi-periphery, from the Southern Cone to East Asia, from Central
Europe to Iberia.

Thanks!

Randy McDonald