Figure 4 is a stacked bar graph demonstrating the changes over time (according to year of death) in the classification of definite and probable TSE cases in Australia by aetiology (sporadic, familial and iatrogenic) from 1970 to 2013. Over the timeframe, a positive trend in the number cases is observed (as depicted in Figure 3.  The graph shows that the large majority (91%) of Australian cases are sporadic, followed by a small proportion of familial cases (7.9%) and iatrogenic cases (1%).