This post aims to improve understanding about the benefits and challenges of using Accident Compensation Corporation (ACC) claims data in the IDI. ACC claims are the most complete and comprehensive source of national statistics on injuries (Statistics New Zealand, 2015).

The aim here is to:

  • describe the ACC claims information currently available in the IDI
  • discuss some of the challenges in using ACC claims data in the IDI and make some suggestions for improvement.


Everyone in New Zealand is covered by ACC’s no-fault scheme if they’re injured in an accident. This includes children, beneficiaries and students. It doesn’t matter if they’re working, unemployed or retired. It also includes visitors to New Zealand. The cover ACC provides helps to pay for the costs associated with recovery. This includes payment towards treatment, help at home and work, and help with income (ACC, 2018).

When a person is injured in New Zealand, they visit a health provider. This could be a doctor, physiotherapist, local medical centre or emergency department at a hospital. The health provider makes the claim to ACC on behalf of the injured person. If the claim is accepted, ACC will pay part of the costs to the health provider (ACC, 2019).

Funding for the scheme is split into five accounts (ACC, 2015). The funding account for a claim can be identified using the variable ‘acc_cla_fund_account_text’.

  • The Work Account, funded by a levy on employers and self-employed workers and shareholder-employees. It covers work injuries for people in paid employment.
  • The Earners’ Account, funded by a levy on earnings. It covers non-work injuries to people in paid employment.
  • The Motor Vehicle Account, funded by a levy included in the price of petrol and the motor vehicle licensing fee. It covers all injuries involving motor vehicles on public roads (including work, earner and non-earner injuries).
  • The Non-Earners’ Account, funded from general taxation. It covers injuries for people not in paid employment. This includes students, beneficiaries, retired people, tourists and children.
  • The Treatment Account, funded by the Earners’ and Non-Earners’ Account. It covers injuries that are caused by, or happen during, medical treatment.

Research using claims data in the IDI can inform us about the risk of injury for different population groups, the impact of injury on future outcomes and the effectiveness of interventions designed to reduce injury.

What data can I find in the IDI?

There are two ACC claims tables in the IDI – an injury table and a medical codes table. The medical codes table includes read codes and ICD codes. Information about the codes can be found in the data dictionary (Statistics New Zealand, 2015).

The injury table contains one row per claim, while the medical codes table may contain multiple rows per claim because an injury can have more than one medical code. Although the injury table is labelled as ‘Serious Injury’ in the data dictionary, it includes all claims, not just those deemed to be serious.

The ACC claims tables use administrative data so they may contain errors. For example, using the accident data and person’s year of birth to estimate their age at the time of the accident produces some unrealistic ages. Data quality is better for entitlement claims (injuries that receive other entitlements such as payments for time off work or specialised treatment) than for medical fees only claims as they are more actively managed (Statistics New Zealand, 2015, page 6).


There are a couple of things to be aware of when using ACC claims data in the IDI.

Each accident is supposed to have one claim number and all future costs associated with that injury are assigned to that claim number. However, within the data it is observed that there are a small percentage of people who have multiple claims with the same accident date as multiple providers may submit a claim to be paid for the same injury. The accident descriptions are very similar, although they are not duplicate rows. After discussion with a staff member at ACC, the author applied a rule in her research whereby each person could have only one accident per day. The claim with the highest costs paid to date was kept for further analysis.  Where this does not uniquely identify a claim, further rules may need to be applied to restrict the dataset to one claim per person per day (Poland, 2018)

The data dictionary states that it only includes claims that have been accepted by ACC (decision ‘accepted’, ‘interim accept’ and ‘pending accept’) (Statistics New Zealand, 2015, page 17). However, there are some work account claims in the IDI that have been declined. It is recommended that declined claims are excluded from the research until such a time as it is clarified whether these are all declined claims or a subset of declined claims. The variable to use for this is ‘acc_cla_decision_text’.


ACC data is an excellent source of New Zealand injury information. Data quality is better for entitlement claims and it is important to be aware that datasets include repeated claims for one event and some claims that have not been accepted by ACC. See references below for further information.


Accident Compensation Corporation (2015). What Your Levies Pay For. Wellington: Accident Compensation Corporation. Available from

Accident Compensation Corporation (2018). What we do. Wellington: Accident Compensation Corporation. Available from

Accident Compensation Corporation (2019). What to do if you’re injured. Wellington: Accident Compensation Corporation. Available from

Poland, M (2018). The determinants of injury compensation claims in a universal claims envrionment. A thesis submitted for the degree of Doctor of Philosophy at the University of Otago, Dunedin, New Zealand.

Statistics New Zealand (2015). IDI Data Dictionary: ACC injury claims data (June 2015 edition). Wellington: Statistics New Zealand. Available from

PDF available here.

Original 10/4/2019, by Michelle Poland (Author) and Zeeman Van Der Merwe (Reviewer).