Questions are being raised over how to tweak immigration policies to get the right net migration levels. 

Stats NZ data is showing a record high net migration gain of 128,900 migrants in the year to October. 

Infometrics Chief Economist Brad Olsen told Mike Hosking that it's difficult to get it right, especially with a near two-year lag between policies and arrivals. 

He says often ministers go too far the other way when they make changes, and two years later neither matches up. 

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