Table 5.

Breakdown of Authorship by Individual Country for All Included Studies (n = 1,242)

Country	1994	1999	2004	2009	2014	2019
Argentina	0 (0.00)	0 (0.00)	2 (0.99)	0 (0.00)	0 (0.00)	1 (0.46)
Australia	0 (0.00)	8 (4.97)	6 (2.96)	9 (3.47)	3 (1.22)	2 (0.91)
Austria	1 (0.65)	2 (1.24)	3 (1.48)	1 (0.39)	1 (0.41)	4 (1.83)
Belgium	1 (0.65)	3 (1.86)	1 (0.49)	1 (0.39)	2 (0.82)	1 (0.46)
Brazil	0 (0.00)	1 (0.62)	0 (0.00)	0 (0.00)	2 (0.82)	1 (0.46)
Canada	5 (3.23)	3 (1.86)	3 (1.48)	6 (2.32)	7 (2.86)	10 (4.57)
Chile	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.41)	2 (0.91)
China	0 (0.00)	0 (0.00)	1 (0.49)	5 (1.93)	9 (3.67)	4 (1.83)
Costa Rica	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.39)	0 (0.00)	0 (0.00)
Croatia	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.39)	0 (0.00)	0 (0.00)
Denmark	2 (1.29)	3 (1.86)	1 (0.49)	0 (0.00)	2 (0.82)	1 (0.46)
Egypt	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.39)	0 (0.00)	3 (1.37)
Finland	1 (0.65)	0 (0.00)	1 (0.49)	1 (0.39)	3 (1.22)	1 (0.46)
France	0 (0.00)	3 (1.86)	0 (0.00)	5 (1.93)	1 (0.41)	2 (0.91)
Germany	2 (1.29)	4 (2.48)	9 (4.43)	12 (4.63)	5 (2.04)	5 (2.28)
Greece	2 (1.29)	0 (0.00)	1 (0.49)	5 (1.93)	0 (0.00)	1 (0.46)
Hong Kong	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.41)	0 (0.00)
Hungary	0 (0.00)	0 (0.00)	1 (0.49)	0 (0.00)	0 (0.00)	0 (0.00)
India	0 (0.00)	1 (0.62)	0 (0.00)	0 (0.00)	1 (0.41)	0 (0.00)
Iran	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.46)
Ireland	2 (1.29)	0 (0.00)	2 (0.99)	0 (0.00)	0 (0.00)	0 (0.00)
Israel	0 (0.00)	4 (2.48)	1 (0.49)	3 (1.16)	4 (1.63)	0 (0.00)
Italy	3 (1.94)	2 (1.24)	6 (2.96)	6 (2.32)	4 (1.63)	1 (0.46)
Jamaica	0 (0.00)	0 (0.00)	1 (0.49)	0 (0.00)	0 (0.00)	0 (0.00)
Japan	3 (1.94)	8 (4.97)	13 (6.40)	9 (3.47)	6 (2.45)	7 (3.20)
Multiple countriesb	2 (1.29)	10 (6.21)	5 (2.46)	12 (4.63)	36 (14.69)	25 (11.42)
Netherlands	0 (0.00)	1 (0.62)	5 (2.46)	2 (0.77)	5 (2.04)	6 (2.74)
New Zealand	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.39)	1 (0.41)	0 (0.00)
Norway	1 (0.65)	0 (0.00)	1 (0.49)	0 (0.00)	1 (0.41)	0 (0.00)
Poland	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.46)
Portugal	0 (0.00)	0 (0.00)	0 (0.00)	2 (0.77)	0 (0.00)	0 (0.00)
Singapore	0 (0.00)	0 (0.00)	1 (0.49)	1 (0.39)	1 (0.41)	0 (0.00)
Slovenia	0 (0.00)	1 (0.62)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)
South Africa	1 (0.65)	0 (0.00)	0 (0.00)	1 (0.39)	0 (0.00)	0 (0.00)
South Korea	0 (0.00)	0 (0.00)	1 (0.49)	16 (6.18)	16 (6.53)	15 (6.85)
Spain	1 (0.65)	2 (1.24)	0 (0.00)	2 (0.77)	1 (0.41)	2 (0.91)
Sweden	4 (2.58)	0 (0.00)	3 (1.48)	1 (0.39)	1 (0.41)	0 (0.00)
Switzerland	0 (0.00)	3 (1.86)	10 (4.93)	11 (4.25)	4 (1.63)	4 (1.83)
Taiwan	0 (0.00)	2 (1.24)	1 (0.49)	2 (0.77)	0 (0.00)	1 (0.46)
Thailand	0 (0.00)	0 (0.00)	1 (0.49)	2 (0.77)	1 (0.41)	1 (0.46)
Turkey	0 (0.00)	1 (0.62)	5 (2.46)	1 (0.39)	2 (0.82)	2 (0.91)
United Kingdom	3 (1.94)	4 (2.48)	6 (2.96)	23 (8.88)	13 (5.31)	4 (1.83)
United States	121 (78.06)	95 (59.01)	112 (55.17)	116 (44.79)	111 (45.31)	111 (50.86)
Total countries	16	20	27	29	28	29

^aValues displayed as n (%).

^bIndicates articles that listed authors from ≥ 2 countries, including United States.