A picture is worth a thousand words, so we will limit to about 250 words to describe the graph.
The net inflow of 10,000 in 2010 dropped to a small net outflow in 2011, driven by the increased flow to Australia after the Christchurch earthquakes, nearly balance by the inflow from Asia, Europe, Americas and elsewhere.
From early 2013 the net outflow to Australia began to evaporate, the inflow from Asia continued at about 20,000 per year and the net inflow from Europe, Americas and elsewhere also continued at 20,000 per year, and so the situation was ripe for 'lift-off'.
By mid-2014 the outflow to Australia was minimal so the other two inflows combined to give a total net inflow of 40,000 per year.
We then had a marketing visit to India to sell our education to their students and that flow drove the lift from mid-2014 to nearly 70,000 by 2016.
Then, just as the student flow faltered, we had the Brexit spectre in Europe, and then the US election. The flow from there increased (assisted by a slack economy in South Africa) to maintain the flow at about 70,000.
All of these combined nicely to give a parabolic rise from early 2013, plateauing at the end of 2016. All three main sources of net inflow appear to have ‘done their dash’ by now, and so unless there is a new ‘shock’ emerging, our maths would indicate that we will be back to a manageable net inflow of 10,000 a year by 2019-2020.
But before then there is a New Zealand election!