The primary EEDI data source was the Shorter Stays in Emergency Department National Research Project (SSED) that investigated the effect of the 6-hour time target policy introduced in Aotearoa New Zealand EDs in 2009. Although the study period does not extend beyond 2012, this dataset provides the most comprehensive and robust ED administrative database available.

A total of 18 (out of 20) DHBs were included in the SSED dataset (two DHBs were not included in the SSED project because of IT restrictions). The SSED project leadership team approved the use of SSED data for the EEDI study.

The SSED dataset was compiled in two stages.

Firstly, all ED visits and non-emergency (elective) hospital presentations during 2006–2012 were identified from the National Minimum Dataset (NMDS), the national collection of public and private hospital discharge and clinical coded information held at the Ministry of Health, with data from 35 hospitals excluded because they did not have an ED

Next, the visit date, patient demographic data and date of death (if applicable) were extracted from the NMDS and linked via unique patient identifiers (NHI number) to the databases held by DHBs to extract holding times for the patient journey (presentation, triage, assessment, admission and discharge times) in each hospital for each event.

Note that ED admissions within the SSED dataset represent individual events rather than individual people.