Besides the requirement that they are positive, we have imposed no other restrictions on the
weights ai. Intuitively,wewould like the weights to increase with the individual’s ranking position
to reflect that more weight is given to individuals who are worse-off. The following condition
ensures this. The principle of health transfers holds if a transfer of health from someone who is
in better health to someone who is in worse health does not lead to a reduction in social welfare
provided the transfer does not change the ranking of the individuals in terms of health.5,6