[FoRK] Micromort, QALY

Stephen Williams sdw at lig.net
Fri Dec 16 21:06:44 PST 2011


Nice confirmation of intuition.  I may have to follow the bib on this some day.
The numbers are obviously those for the US.  It would be extremely interesting to carefully measure the same things all over the 
world.

Artificial Intelligence: A Modern Approach, Third Edition

16.3.1 Utility assessment and utility scales
...
In medical, transportation, and environmental decision problems, among others, people's lives are at stake.  In such cases, 
u{floor} is the value assigned to immediate death (or perhaps many deaths).  Although nobody feels comfortable with putting a 
value on human life, it is a fact that tradeoffs are made all the time.  Aircraft are given a complete overhaul at intervals 
determined by trips and miles flown, rather than after every trip.  Cars are manufactured in a way that trades off costs against 
accident survival rates.  Paradoxically, a refusal to "put a monetary value on life" means that life is often undervalued.  Ross 
Shachter relates an experience with a government agency that commissioned a study on removing asbestos from schools.  The 
decision analysts performing the study assumed a particular dollar value for the life of a school-age child, and argued that the 
rational choice under that assumption was to remove the asbestos.  The agency, morally outraged at the idea of setting the value 
of a life, rejected the report out of hand.  It then decided against asbestos removal, implicitly asserting a lower value for 
the life of a child than that assigned by the analysts.

Micromort
Some attempts have been made to find out the value that people place on their own lives.  One common "currency" used in medical 
and safety analysis is the micromort, a one in a million chance of death.  If you ask people how much they would pay to avoid a 
risk -- for example, to avoid playing Russian roulette with a million-barreled revolver -- they will respond with very large 
numbers, perhaps tens of thousands of dollars, but thier actual behavior reflects a much lower monetary value for a micromort.  
For example, driving in a car for 230 miles incurs a risk of one micromort;  over the life of your car -- say, 92,000 miles -- 
that's 400 micromorts.  People appear to be willing to pay about $10,000 (at 2009 prices) more for a safer car that halves the 
risk of death, or about $50 per micromort.  A number of studies have confirmed a figure in this range across many individuals 
and risk types.  Of course, this argument holds only for small risks.  most people won't agree to kill themselves for $50 million.

QALY
Another measure is the QALY, or quality-adjusted life year.  Patients with a disability are willing to accept a shorter life 
expectancy to be restored to full health.  For example, kidney patients on average are indifferent between living two years on a 
dialysis machine and one year at full health.

sdw



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