Conclusion
The study strongly suggests that for people on low incomes, even small co-payments with a low ceiling can result in use of more expensive healthcare. In New Zealand, we strongly recommend that the $5 prescription co-payments be removed for those with high health needs and low incomes, or be scrapped entirely. The latter solution would be administratively simpler and avoid the risk that those with very high needs miss out because they do not successfully navigate bureaucratic processes [Further research should examine other small charges for healthcare that may have perverse consequences for healthcare funders and increase inequities. RCTs are expensive but not prohibitively so when the charges themselves are low.