What I should have known, but didn't, is that Stats was already on the case, and already produces comprehensive data on the sources of direct investment. What's more, the official data are based on actual investments (the KPMG analysis is based on approvals of intended investments, which may not be carried through, though most will be), and also cover investments from Australia that don't turn up in the OIO data (because Aussie investors typically don't have to go through the OIO hoops for investments worth less than $477 million). There is one wrinkle - the data show the FDI by country of immediate investor, rather than by country of ultimate owner - and Stats tell me they're looking into the possible implications of that, but otherwise this is the heavy duty source of FDI info.
If you want to explore the official data yourself, you can start here, or you can go to Infoshare: select 'Economic indicators' and then 'International Investment Position', where you'll find a bunch of 'directional basis' statistics at the top of the list (I fell into a heffalump trap when I first went looking, hence the roadmap). In any event I've summarised the latest data for you in the graphs below.
The first one shows the major inwards flows of FDI for the two-year period to March '14 (partly overlapping with the KPMG timeframe), and the other shows the outstanding stock of FDI in March '14. The data for the year to March '15, by the way, aren't far away (September 24).
I have little or no sympathy with anti-FDI agitation, which mostly seems to me either unpleasant or misguided. But putting that aside, and just looking at the facts, they don't show the Asian takeover that critics have been frothing about. The largest inflows in the past few years have come from the UK and Australia: Hong Kong's third, but some distance behind. And over time, far and away the largest direct investor into New Zealand has been Australia, followed by decent but much smaller chunks from the US and the UK.
Not that the facts ever get in the way of the xenophobes' ravings.