Not sure on the 1.5% from New Zealand.  New Zealand is spending around 1.3% maybe 1.35% of GDP and this is not counting the $20 Billion over 15 years, people think this is part of the Defence budget. It isn't, this $20B is separate and over and above of the actual defence budget. But the they may have added this to the budget to get 1.5%

Australia is spending around 1.8% - 1.9% and increasing it to over 2% over the next few years. This is to counter China's growing expansion and threat. Some also say this is one of the reasons the National Government at the time devoted the $20b to defence as well.

Above figures are from Wikipedia which least be honest here are not to be trusted on the best of days. Other figures from SIPRI

There are a few things to consider when you see comparisons in defence budgets or spending... or any spending for that matter. I see it mentions all they time... For example {enter country name here} spends "x amount" and New Zealand spends "x amount", how come New Zealand doesn't have XYZ and {enter country name here} does... 

First thing to consider is how strong each countries dollar is comparatively. If {enter country name here} dollar is stronger than New Zealand's dollar you are going to get more bang for your buck. You have to remember that this is always changing and evolving as is inflation.

Now think what the budget is being spent on... example, how many personal are in the defence force, and what are their pay packets comparatively, Western countries will most likely pay their soldiers, sailors and airmen more than say a country like the Philippines. (Please this is just an example and I don't know how much they get paid in the  Philippines armed forces) 

Also think of alliances and where {enter country name here} where they buy equipment from... Indonesia may buy equipment from Russia which may be cheaper in many examples... but the chances New Zealand buying Russian or Chinese equipment is next to zero chance if not slightly less than zero and will only only buy european or american equipment.

You also have to remember defence budgets would only grow with a percentage of GDP only if there is growth with the GDP. If GDP is staggant or in a negative then that percentage is still less money and may seem as a cut back, and to keep all as normal extra money may need to be added to the budget to cover costs which in the books appears as an increase when in reality it is not.

Finally what kind of defence industry does {enter country name here} compared to the non-existent industry here in New Zealand.  Example Indonesia has a ship-building industry and building your own equipment can save time and (sometimes) money if done correctly... New Zealand doesn't have this capability. Government spend money into its own economy does help growth. However most government spending like this can many times get out of hand.