This chart shows the number of total sites in each continent over the years:
| Year | Europe | Asia | Africa | Oceania | North America | South America |
| 1978 | 3 | 0 | 3 | 0 | 4 | 2 |
| 1979 | 23 | 6 | 15 | 0 | 8 | 2 |
| 1980 | 31 | 12 | 24 | 0 | 11 | 3 |
| 1981 | 38 | 15 | 30 | 3 | 17 | 4 |
| 1982 | 40 | 19 | 40 | 5 | 20 | 5 |
| 1983 | 55 | 23 | 42 | 5 | 24 | 9 |
| 1984 | 62 | 30 | 45 | 5 | 27 | 12 |
| 1985 | 71 | 42 | 49 | 5 | 28 | 16 |
| 1986 | 87 | 49 | 52 | 6 | 28 | 18 |
| 1987 | 99 | 61 | 55 | 7 | 38 | 20 |
| 1988 | 108 | 68 | 60 | 9 | 41 | 21 |
| 1989 | 110 | 69 | 63 | 9 | 41 | 21 |
| 1990 | 118 | 71 | 64 | 11 | 42 | 23 |
| 1991 | 126 | 79 | 66 | 12 | 43 | 24 |
| 1992 | 137 | 84 | 67 | 13 | 45 | 24 |
| 1993 | 153 | 95 | 67 | 13 | 48 | 27 |
| 1994 | 165 | 105 | 69 | 14 | 49 | 30 |
| 1995 | 179 | 111 | 70 | 14 | 52 | 35 |
| 1996 | 202 | 118 | 74 | 14 | 53 | 35 |
| 1997 | 226 | 126 | 79 | 16 | 59 | 36 |
| 1998 | 245 | 132 | 79 | 18 | 61 | 37 |
| 1999 | 266 | 142 | 84 | 18 | 68 | 43 |
| 2000 | 296 | 156 | 87 | 19 | 70 | 52 |
| 2001 | 310 | 161 | 92 | 19 | 71 | 55 |
| 2002 | 313 | 163 | 93 | 19 | 72 | 56 |
| 2003 | 321 | 172 | 97 | 20 | 73 | 58 |
| 2004 | 337 | 183 | 101 | 21 | 75 | 58 |
| 2005 | 346 | 191 | 104 | 21 | 77 | 59 |
| 2006 | 351 | 196 | 109 | 21 | 78 | 60 |
| 2007 | 358 | 202 | 112 | 22 | 80 | 60 |
| 2008 | 367 | 211 | 114 | 25 | 82 | 60 |
| 2009 | 372 | 215 | 116 | 25 | 82 | 61 |
| 2010 | 375 | 225 | 118 | 28 | 85 | 62 |
| 2011 | 381 | 235 | 122 | 29 | 87 | 63 |
| 2012 | 387 | 246 | 126 | 30 | 88 | 64 |
| 2013 | 393 | 254 | 128 | 31 | 90 | 64 |
| 2014 | 399 | 270 | 129 | 31 | 92 | 65 |
| 2015 | 407 | 282 | 129 | 31 | 95 | 66 |
| 2016 | 412 | 292 | 131 | 32 | 98 | 67 |
| 2017 | 417 | 302 | 134 | 33 | 98 | 69 |
| 2018 | 423 | 310 | 136 | 33 | 100 | 70 |
| 2019 | 435 | 322 | 137 | 34 | 102 | 71 |