There have been steady improvements in the modelling methodology used by UNAIDS/WHO and partners, along with better data from country surveillance. These have led to lower global AIDS estimates, not just for the current year but also for past years, despite the continued expansion of the global epidemic. Current estimates therefore cannot be compared directly with estimates from previous years, nor with those that may be published subsequently.
UNAIDS and WHO continue to work with countries, partner organizations and experts to improve data collection. These efforts will ensure that the best possible estimates are available to assist governments, non-governmental organizations and others in gauging the status of the epidemic and monitoring the effectiveness of prevention and care efforts.