Top countries in space sciences

	Country	Papers	Citations	Impact
1	Scotland	2,319	52,710	22.73
2	Israel	1,570	31,822	20.27
3	Canada	5,729	111,737	19.50
4	Chile	3,322	62,653	18.86
5	United States	55,539	1,039,395	18.71
6	The Netherlands	5,827	108,303	18.59
7	Denmark	1,511	27,991	18.52
8	England	15,968	293,401	18.37
9	Australia	4,990	89,928	18.02
10	Switzerland	2,959	51,649	17.45
11	Germany	17,572	304,158	17.31
12	Italy	11,944	186,411	15.61
13	Sweden	2,147	32,765	15.26
14	France	13,977	203,653	14.57
15	Spain	7,017	96,634	13.77
16	Japan	8,797	117,883	13.40
17	Poland	2,683	35,198	13.12
18	Mexico	2,376	28,985	12.20
19	Russia	8,567	59,669	6.96
20	China	6,022	36,777	6.11

The data above were extracted from the Essential Science Indicators database of Thomson Reuters. This database, currently covering the period January 1999 through June 2009, surveys only journal articles (original research reports and review articles) indexed by Thomson Reuters. Articles are assigned to a category based on the journals in which they were published and the Thomson Reuters journal-to-category field-definition scheme. Both articles tabulated and citation counts to those articles are for the period indicated. Here our ranking in space sciences, including astronomy and astrophysics, is by citations per paper among nations that collected 25,000 or more citations during the period to reveal weighted impact. For articles with multiple authors from different nations, each nation receives full, not fractional, citation credit. Essential Science Indicators lists nations ranked in the top 50 per cent for a field over a given period, based on total citations. In space sciences, 69 nations are listed, meaning 138 were surveyed. Twenty nations collected at least 25,000 citations in this field during the period. For more information on Thomson Reuters Essential Science Indicators, see http://scientific.thomsonreuters.com/products/esi