Matai is a short- to medium-term macroeconomic forecasting model written in Eviews which is used by the Treasury to aid the production of its economic and tax forecasts.
The economic forecasts not only form the basis for projections of tax revenue, but also inform the Government of the economic environment that the fiscal policy settings are expected to operate in.
Short descriptions of Matai can be found at:
https://treasury.govt.nz/publications/mei/monthly-economic-indicators-march-2018-html#section-4
https://treasury.govt.nz/publications/efu/budget-economic-and-fiscal-update-2018-html#child-2
A more detailed description is planned to be released during 2019. While the current model version is being calibrated, a formal estimation is currently underway which should also be completed next year.
At some stage in the future, the full model code and data may be made available on this site, allowing the public to replicate the published forecasts with the model and run their own scenarios.
Matai was first used in the production of the 2018 Budget Economic and Fiscal Update. It replaced the New Zealand Treasury Model (NZTM) which had been in use for over ten years.
For a description of NZTM, see:
https://treasury.govt.nz/publications/wp/introduction-new-zealand-treasury-model-wp-09-02