The short answer is "probably Switzerland".
Now, NZ has produced a total of 3 Nobel Prize winners. Ernest Rutherford, Maurice Wilkins and Alan MacDiarmid (http://en.wikipedia.org/wiki/List_of_Nobel_laureates_by_country), each of whom NZ educated and then shipped off to either the UK or US where they performed their magnificent research. Therefore I split the Nobel Prize counts into "employing country" and raw totals from the Wikipedia entry.
Hungary, UK, Switzerland, NZ and Denmark are very efficient countries in terms of producing Nobel Prize winners.
Switzerland, UK, Denmark, Hungary and the Netherlands are very efficient at employing and investing in Nobel Prize winning research. These countries have been doing something right!
Wouldn't it be nice if one day a NZer was awarded a Nobel for research they actually conducted in NZ?
Raw data and higher quality images are available here: