| Year Joined | Nation | % Correct |
|---|---|---|
| 1949 | United States | 97%
|
| 1949 | United Kingdom | 96%
|
| 1949 and 2009 | France | 95%
|
| 1982 | Spain | 94%
|
| 1955 | West Germany | 94%
|
| 1949 | Canada | 88%
|
| 1949 | Portugal | 88%
|
| 1949 | Norway | 87%
|
| 1999 | Poland | 87%
|
| 1949 | Italy | 86%
|
| 1952 | Greece | 83%
|
| 1949 | Belgium | 80%
|
| 1949 | The Netherlands | 78%
|
| 2004 | Latvia | 77%
|
| 1952 | Turkey | 77%
|
| 2004 | Estonia | 76%
|
| 1949 | Denmark | 75%
|
| 2004 | Lithuania | 74%
|
| 2004 | Slovakia | 71%
|
| 1999 | Czechia | 70%
|
| 2004 | Slovenia | 69%
|
| 1999 | Hungary | 68%
|
| 2009 | Croatia | 67%
|
| 1949 | Luxembourg | 67%
|
| 2004 | Romania | 67%
|
| 1949 | Iceland | 66%
|
| 2004 | Bulgaria | 63%
|
| 2009 | Albania | 62%
|
| 2017 | Montenegro | 53%
|
| 2020 | Northern Macedonia | 53%
|