4. Discussion
The changing average LOS of Japanese hospitals over the last four decades differs from those of other developed countries (Fig. 1a). It is generally believed that the steep decline seen since the 1980s has been a distinct response to cost-containment policies targeted at reducing LOS [19–21]. However, Japan’s hospital sector is characterised by its diversity of ownership types [22,23], and we have revealed the diverse paths of average LOS accord- ing to ownership-type groups that is behind this decline. Our hierarchical cluster analysis produced a cluster of public hospitals and a cluster of private hospitals, while the national government cluster has a path of its own (Fig. 2). Our joinpoint regression analyses produced contrasting differences among the three clusters (Fig. 1b). In particular, the analysis of the private cluster is different from those of the public or national government clusters, or the paths seen in other developed countries.