Median personal income over time

Ok - over the past couple of hours I've been doing a bit of number crunching in response to a post on median wage increases over at kiwiblog. First up, I have a few contentions with David's analysis. Specifically they are ....

A) He provides no links to his sources, and gives no account of his methodology, which means his results are dubious at best.

B) He only measures increases in the median wage of full time workers - this leaves out around 40% of the working age population - so to me this is hardly a useful measure of how ordinary New Zealanders have fared comparatively under National and Labour.

As such, in my assessment I've used the median income of the entire working age population (provided by the 1991, 1996, 2001 and 2006 census data) - and I provide links to my sources, and a run through of my (simple) methodology, so my results can be replicated by whoever pleases.

So my findings were that "median personal income" in New Zealand rose at an average rate of 1.4% during the decade of 1991-2001 (roughly National's time in power) and 3.26% during the period of 2001-2006 (roughly Labour's time in power so far).

So, how did I arrive at these figures? Well - first I got the census data, which can be found here:

http://www2.stats.govt.nz/domino/external/pasfull/pasfull.nsf/00c9e0a06fee31764c2568470008f782/4c2567ef00247c6acc256c2f00139bf1?OpenDocument

and here (this link was too long so I had to cut it half - really need to learn that html coding stuff):

http://www.stats.govt.nz/census/2006-census-data

/quickstats-about-incomes/quickstats-about-incomes.htm?page=para002Master

Then I adjusted these figures for tax:

I deduced the 1991 and 1996 tax rates (19.29%) from David Farrar's post.

http://www.kiwiblog.co.nz/2007/10/

how_has_the_average_worker_done_under_labour.html#comments

And I calculated the after tax figures for 2001 and 2006 using this official IRD tax calculator.

https://www.ird.govt.nz/cgi-bin/form.cgi?form=incrates

Then converted all of the after-tax figures into 2006 dollars using this CPI calculator:

http://www.rbnz.govt.nz/statistics/0135595.html

And vola - there you have it.

(hat-tip: Sam Dixon)

Yet another reason why New Zealand needs its unions back

Well as statistical associations go it doesn't get much clearer. Workers who live in countries with strong unions work shorter hours and vice versa - period. In case anyone is wondering, New Zealand is one of the dots down the bottom right of the graph. Our "hours worked" figure is 1767 (6th highest out of the 20 countries), and our collective bargaining coverage is 27.5 % (3rd lowest in the OECD).
Sources:

http://en.wikipedia.org/wiki/Image:Yearly_working_time.jpg

https://www.oecd.org/document/12/0,3343,en_2649_201185_31781132_1_1_1_1,00.html

So it's established then: National's De-unionisation of New Zealand in the 1990s has created an economy that's characterised by low wages, low productivity levels and long working hours. If only the Labour party had the courage of conviction to turn this around.