Sunday, 8 October 2017

Hospital emergency departments follow Goodhart's law

Goodhart's law states that "When a measure becomes a target, it ceases to be a good measure". In other words, when you reward (or punish) behaviour based on some targeted measure, people will game the system to ensure you get more (or less) of whatever is being measured, regardless of whether it is what you intended. Which brings us to this story on New Zealand hospital emergency departments from earlier this week:
Wait times dropped after emergency department time targets were introduced but a report has found some hospitals shuffled patients around just to meet the target.
A University of Auckland-led study published in BioMed Central Health Services Research studied emergency department (ED) waiting times at four New Zealand hospitals between 2006 and 2012.
With hospitals under pressure, a target measure was introduced in an effort to minimise crowding, which left some patients in hospital corridors.
Official DHB reports found most EDs met the 95 per cent target to be seen, treated or discharged within six hours. However, the introduction of "short-stay units" in the last 10-years has seen researchers question those reports.
Hospitals record the length of stay in EDs, but shifting patients into the short-stay units isn't counted in reported ED figures...
Associate Professor of the University of Auckland's School of Population Health Dr Tim Tenbensel said moving patients to the short-stay-units was reasonable in most cases...
"Having patients in these short-stay units is certainly preferable to having them wait in hospital corridors as was common before 2009.
"However, we know from our interviews that there were some instances where the only reason patients were transferred to short-stay was to avoid breaching the target." 
The most surprising thing about this was that no one appears to have foreseen this possibility before the target. Every time a target is introduced, someone really needs to think about the answer to the question, "If I had to meet this target, what would be the lowest cost way for me to do so?", since that's effectively what the decision-makers faced with meeting the target are going to do. I guess we are fortunate that the unintended consequence in this case didn't make things any worse.

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