  The impact of astronomical research carried out by different countries has
been compared by analysing the 1000 most-cited astronomy papers published
1991-8 (125 from each year). 61% of the citations are to papers with first
authors at institutions in the USA, 11% in the UK, 5% in Germany, 4% in Canada,
3% in Italy and 3% in France. 17% are to papers with first authors in ESO
countries. The number of citations is approximately proportional to the number
of IAU members in a given country. The number of citations per IAU astronomer
is highest in the USA, Switzerland and the UK. Within continental Europe, the
number of citations per IAU astronomer varies little from country to country,
but is slightly higher in the north than in the south. The sample of 1000
papers maps regional subject preferences. 62% of the extragalactic papers in
the sample were published from the USA, 15% from the UK, 23% from other
countries (mainly in continental Europe). 62% of the papers on stars were also
published from the USA, but the fractions from the UK and from other countries
are 2% and 36% respectively.
