Fig. 3

Trend and seasonal variation in rates of hospital-acquired pressure ulcers (HAPUs). Trend is represented by the trajectory of annual mean rate and seasonal variation is represented by the trajectory of (quarterly rate – annual mean rate); rates were aggregated over units within 41 groups. The thick line in each plot is for the group of 848 units with all 36 quarters of data in 2004–2012. Each vertical dash line denotes the fourth quarter of a year