Background
In New Zealand and elsewhere, there are socio-economic and ethnic disparities in use of medicines [Most studies of the impact of patient payments for prescription medicines are observational. These have found increasing co-payments can lead to lower use of medicines [Existing studies rarely include the option of zero co-payments. Wales, Scotland and Northern Ireland have introduced free prescriptions, but quantifying the impact of this is complex, in part because most prescriptions (particularly those for people with high health needs or low income) were exempt from co-payments even before the change [