| Value | Category | 
                                    
                    
                        | 1 | 2001 | 
                                    
                    
                        | 2 | 2002 | 
                                    
                    
                        | 3 | 2003 | 
                                    
                    
                        | 4 | 2004 | 
                                    
                    
                        | 5 | 2005 | 
                                    
                    
                        | 6 | 2006 | 
                                    
                    
                        | 7 | 2007 | 
                                    
                    
                        | 8 | 2008 | 
                                    
                    
                        | 9 | 2009 | 
                                    
                    
                        | 10 | 2010 | 
                                    
                    
                        | 11 | 2011 | 
                                    
                    
                        | 12 | 2012 | 
                                    
                    
                        | 13 | 2013 | 
                                    
                    
                        | 14 | 2014 | 
                                    
                    
                        | 15 | 2015 | 
                                    
                    
                        | 99 | Don't remeber | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.