Modelled Territorial Authority Gross Domestic Product for New Zealand

Peter Ellis

June 2016

Today’s content

  • Modelling TA GDP
  • Accessing the data
  • Example analysis

Modelling TA GDP

The Challenge

  • Consistent with National and Regional Tier 1 GDP
  • Detailed data available for re-use
  • Source code and method open for critique and improvement
  • Easy interactive access

The data

  • Business Demography Statistics
  • Linked Employer - Employee Database
  • Regional GDP
  • National GDP

The method (bottom up)

  • reconcile the various earnings measures
  • scale up employee numbers to earnings
  • scale up earnings to GDP

The method (alternative, top down version)

  • reconcile the two GDP measures
  • allocate any ambiguity on basis of earnings
  • allocate any remaining ambiguity on basis of employees

sankey

Commuter correction

  • earnings only published by place of residence
  • use the Census 2013 to reallocate earnings on basis of commuting
  • known area for future improvement

Assumptions

  • Earnings a good indicator of value added
  • Employee numbers a good indicator of earnings
  • No interaction between TA and earnings:GDP ratio for specified industry
  • No interation between Region/TA and inter-industry relative earnings:GDP ratios of industries
  • Commuter patterns unchanging and not industry-specific
  • Price movements not industry-specific
  • Price movements not region-specific

Accessing the data

rear

webtool

download

source

Example analysis

map1

More detailed example

Question

Do either of this variables in 2005 have an impact on the next ten years of growth:

  • Agricultural importance
  • GDP per capita

aglines

Modelling approach

  • Generalized additive model
  • Degrees of freedom allocated to variables based on strength of Spearman \(\rho^2\)
  • Smoothed two dimensional spline to control for spatial correlation

Strength of relationships

spearman

\[ GDPGrowth_i = \beta_0 + \beta_1 \times PropAg2005 +\\ \beta_2 \times GDPpp2005 + \beta_3 \times s(lat, long, 5) + \epsilon_i\]

  • no evidence of an agriculture in 2005 effect
  • no evidence of a GDP per capita in 2005 effect
  • strong spatial effect

The spatial effect

contourmap