Improved survival in severe sepsis over last 12 years

Despite no ‘breakthroughs’ in severe sepsis therapy there has been more than a creeping improvement in survival rate over the last 10 years (at least in Aus, NZ & Finland). Mortality rate 35% reduced to 18%. Presumably this is largely though doing less harm and attention to basics. Where does this leave us in interpreting studies with higher rates of death from even just a few years ago?