| Year | Number of strikes | Number of workers involved | Working hours not worked, thousands |
|---|
| 1991 | 3 | 24 148 | 76.0 |
| 1992 | 4 | 1 010 | 33.0 |
| 1993 | 5 | 2 574 | 42.0 |
| 1994 | 4 | 31 529 | 229.0 |
| 1995a | 7 | 172 048 | 1 708.0 |
| 1996 | 8 | 4 491 | 19.0 |
| 1997 | 5 | 853 | 15.0 |
| 1998 | 7 | 1 447 | 3.0 |
| 1999 | 5 | 16 685 | 242.0 |
| 2000 | 5 | 26 978 | 1 192.0 |
| 2001 | 6 | 21 128 | 61.0 |
| 2002 | 4 | 4 573 | 9.0 |
| 2003 | 7 | 10 831 | 19.0 |
| 2004 | 8 | 6 276 | 116.0 |
| 2005 | 11 | 1 425 | 7.0 |
| 2006 | 16 | 24 665 | 52.0 |
| 2007 | 13 | 64 612 | 186.0 |
| 2008 | 8 | 8 633 | .. |
| 2009 | 9 | 3 134 | 8.6 |
| 2010 | 7 | 3 263 | 133.1 |
| 2011 | 1 | … | … |
| 2012 | 3 | 1 885 | 4.6 |
| 2013 | 1 | … | … |
| 2014 | – | – | – |
| 2015 | 2 | … | … |
| 2016b | 7 | 39 101 | 270.5 |
| 2017 | 5 | 6 706 | 30.4 |
| 2018b | 6 | 15 535 | 289.4 |
| 2019b | 12 | 20 905 | 416.3 |
| 2020 | 2 | … | … |