In the final of the series, immigration reporter Lincoln Tan looks at how well the country retains its foreign residents.
One out of five people granted New Zealand permanent residency between 2002 and 2008 is absent from the country.
According to the Department of Labour, 83,983 of the 452,500 granted residency over the period are living permanently outside New Zealand.
Despite not residing in New Zealand, these absent permanent residents - whom migrant advisers say were granted residency mainly through the business stream - will still be eligible for health and education subsidies should they decide to return.
Should they maintain their residency status, their children could also be entitled to New Zealand residency, which will make them also eligible for these subsidies.
Migrant advisers have raised questions whether this allows migrants to use New Zealand as a "second option" for retirement, as a springboard to Australia or use its services without contributing to the economy.
Immigration Minister Jonathan Coleman said permanent residents must generally remain here for two years to become eligible for an indefinite returning resident's visa - which must be renewed each time they replaced their passport.
"The returning resident visa status of secondary applicants, such as children, is dependent upon whether the principal applicant maintains the status."
Dr Coleman says business migrants, by nature, would be able to move between countries with ease.
"I would note that (business) migrants are mobile, many have skills in high demand, so a proportion of them will move on to other countries or return to their source country."
Dr Coleman said the OECD has recognised New Zealand did as well as Canada and the US, and better than European countries, at retaining immigrants.
"Research shows that in general, business migrants are focused on establishing successful enterprises in New Zealand, and that they tend to be more profitable than similar-sized New Zealand firms."
But business analyst Keng Lim says the fact a fifth of immigrants chose overseas showed they are not committed to New Zealand, and wanted permanent residency only as a "stand by option" or for "personal gain" - such as sending their children to New Zealand schools as domestic students.
The highest levels of resident absenteeism are from Taiwan (50 per cent), Hong Kong (40 per cent) and Singapore (37 per cent). At the other end of the scale were Tonga and Afghanistan (both 5 per cent).
"It shows that migrants from richer countries want residency so they can send their children here for free education, and hold on to their residency as a retirement option, rather than wanting to actively contribute to the economy," said Mr Lim.
"With the high taxation here, many know they are better off elsewhere, but being able to get an indefinite residency makes New Zealand more attractive than Australia."
He said some would also use their New Zealand residency as a way to get into Australia.
Association for Migration and Investment chairwoman Coral Wong says she has, in a personal capacity as an immigration adviser, acted for "many clients" before 2005 wanting permanent residency mainly to get their children into New Zealand schools.
Then, people who could prove they have $1 million to invest could be granted residency.
But policy changes were made in November 2005, doubling the investment amount to $2 million and requiring investors to put their money in a Government infrastructural fund for five years.
Investor numbers dropped drastically when the Labour Government raised the minimum amount in 2007 to between $2.5 million and $20 million, depending on the age of the potential migrant.
Last July, National introduced the new Migrant Investor Policy, aimed at attracting financial capital by granting residence to those who wished to make significant financial contribution to New Zealand's economy.
It also launched the Entrepreneur Plus policy in November, fast tracking residency for migrants who create at least three fulltime jobs and invest $500,000 in their business.
Last year, 46,097 people were granted permanent residence with 62 per cent coming through the Skilled and Business Stream.
But Labour MP Raymond Huo, who is planning to submit a Private Members' Bill to make changes to alter the business policies, says National's new business policy is "just a bad joke".
Mr Huo says to keep skilled and business migrants in the country, the Government must invest in better infrastructure to support them and the businesses that they start here.
Long-term absence for migrants approved for residence between 2001 to 2008 (top 10):
1. Taiwan: 2679 / 50 per cent
2. Hong Kong: 1132 / 40 per cent
3. Singapore: 1107 / 37 per cent
4. Indonesia: 1160 / 31 per cent
5. Canada: 1204 / 30 per cent
6. Malaysia: 2593 / 29 per cent
7. United States: 3511 / 29 per cent
8. Pakistan: 527 / 26 per cent
9. China: 14,868 / 25 per cent
10. Somalia: 519 / 25 per cent
21. United Kingdom: 14,650 / 16 per cent
22. South Africa: 6022 / 16 per cent
Total: 83,983 / 19 per cent