| Year | Number of sites | Area (ha) |
|---|---|---|
| 2001 | 1461 | 1593000 |
| 2002 | 1467 | 1569100 |
| 2003 | 1467 | 1583000 |
| 2004 | 1457 | 1634900 |
| 2005 | 1445 | 1728800 |
| 2006 | 1441 | 1726100 |
| 2007 | 1287 | 1577700 |
| 2008 | 1299 | 1575800 |
| 2009 | 1285 | 1595700 |
| 2010 | 1296 | 1595100 |
| 2011 | 1302 | 1591900 |
| 2012 | 1220 | 1570000 |
| 2013 | 1213 | 1615500 |
| 2014 | 1231 | 1722700 |
| 2015 | 1265 | 1825600 |
| 2016 | 1287 | 1798700 |
| 2017 | 1285 | 1811600 |