text: **7.4 Data and research – major evidence difficulties at EU level**
  A precise and — in some cases**even an approximate — assessment of the state of OSH**is by far 
  not an easy task. 481 Often, different explanations and reasons for similar developments are given, 
  diverging or opposite developments in some countries are not well explained, and finally we can observe 
  — for the same topic or situation — also a highly positive and highly negative assessment of the state 
  of OSH in general or of several aspects, simply because there are no data that all stakeholders accept 
  as reliable.**One example might be the level of compliance:**estimates of the number of breaches of 
  OSH legislation and the responsibility for these breaches will often differ between employers and 
  workers. 
  
  As mentioned already, several groups are**hard-to-reach**in surveys or other types of research, for 
  example,**migrants, seasonal and posted workers due to language issues**and**‘cultural’ and**
  **contract insecurity,**and**workers in irregular circumstances,**but also**workers with a legal**
  **exemption from several OSH regulations**, for example, self-employed, often military and police and 
  some parts of the public sector. Literature and analysis adds to these ‘old-hard-to-reach’ groups of 
  workers the**‘new-hard-to-reach’**, which are mainly characterised by new types of contracts, a less clear 
  employer / employee role, and/or mobile and remote work.482 