In many countries, deaths are certified by doctors and certification data is collected. This enables historic statistical analyses, for example in the UK revealing the virtual eradication of deaths from infectious diseases (e.g. tuberculosis) and the sharp reduction in deaths from cardiovascular diseases (e.g. heart disease, strokes). However, the data has its limitations because the recorded cause of death may be unreliable. For example by recording the ultimate cause (e.g. pneumonia) rather than the underlying cause (e.g. old age or AIDS). International standards for classifying deaths are used in an attempt to bring greater consistency to recording practices.