Showing posts with label Simon Collins. Show all posts
Showing posts with label Simon Collins. Show all posts

Thursday, 18 June 2015

Racial bias in mortgages?

Simon Collins at the Herald asked me for comment on a paper alleging racial bias in mortgage lending; his story's now up.

The paper is available here. It shows, using ordered logit regression, that people who self-identify as being more easily identified as Maori are less likely to own their own home, correcting for income and a few other variables. The paper's empirics say absolutely nothing about mortgages or banks. But the study nevertheless concludes:
"To sum it up in one sentence: results from a large national probability sample of Māori indicate that the more Māori you look, the less 'mortgage worthy' you are."
Here are a few alternative hypotheses:
  • The empirics correct for current employment and current income but not past employment and past income. If Māori employment histories are more varied than non-Māori, and if this also follows the "is identified as Māori " indicator, Māori will have less accumulated wealth at any given level of income, and this is not controlled in the study.
  • If those who look more Māori are given preference in state housing, then home ownership would also be attenuated.
  • If parental resources are negatively correlated with looking more Māori , then that also affects ability to put together a deposit on a house. Note too the potential influence of holding household wealth under Māori land tenure.
I also think they've an error in how they described the magnitude of the effect. Remember that this is an ordered logit regression. So you can't just take the point estimate and multiply it by the number of interval steps to get an accumulated effect; you have to ask your stats package to give you a predicted value at the different values of the category. At page 11, it really looks like they linearised from the point estimate:
Some readers may be wondering how large this effect is in practical terms. One way to think about it is like this: when statistically adjusting for numerous other demographics, such as differences in income, region of residence, and education, a Māori person with a score of 5.55 on our Perceived Appearance measure of Māori identity would be twice as likely to not own their home relative to someone with a score of 1 in Perceived Appearance. This is a statistically significant association, which in our view represents a large and extremely important difference in the rate of home ownership based solely on merely appearing more Māori.
They have an odds ratio of 0.82, which ought to mean that a step change increase in perceived appearance score from the mean score reduces likelihood of owning a home by 18%. I don't think that means that if you go 5.55 steps in the other direction (1/0.18) from the mean score doubles your likelihood of home ownership, except under some pretty strong assumptions. But it's been a little while since I've played around in ordered logit.

Here's the bit where Collins quoted me - entirely fairly:
However Dr Eric Crampton of the NZ Initiative think-tank said there could be many other explanations for this besides racial bias. For example, people who looked more Maori might have parents who did not have freehold properties to use as collateral for loans, a factor that was not surveyed.
"Banks would be throwing money away if they decided to not lend to somebody simply based on looks," he said.
Mortgage brokers Bruce Patten in Auckland and Karen Essex-Mooney in Blenheim both said they had never seen a mortgage application turned down because the borrowers were Maori. They said many borrowers now applied online and never actually met the lenders.
New Zealand Bankers' Association chief executive Kirk Hope said racial stereotyping was not in the banks' or their customers interests especially within such a competitive part of the banking sector.

Tuesday, 11 November 2014

Big numbers: domestic violence edition

Simon Collins at The Herald reports on some problems in Suzanne Snively's estimates of the social costs of domestic violence.
Sir Owen Glenn's family violence inquiry has stumbled again, producing a $7 billion estimated cost of family violence based on the mis-reading of a key research paper.
A report by economist Suzanne Snively and Wellington theatre student Sherilee Kahui, published by the inquiry yesterday, said family violence cost New Zealand between $4.1 billion and $7 billion a year - up from Ms Snively's last estimate in 1994 of just $1 billion.
It looks like they attributed the full high-end costs to the greater number of people experiencing more moderate forms of abuse. This isn't to diminish that experience, but there are gradations of experience and gradations of cost.
Inquiry spokeswoman Marie McNicholas declined to comment on the latest mistake and referred questions to Ms Snively. Ms Snively said the data was prepared by Ms Kahui.
Ms Kahui said the $7 billion "high-end" figure was not in an early version of the study, which initially included only the "low-end" estimate of $4.1 billion and what is now described as a "moderate scenario" of $4.5 billion.
The high-end estimate was added after experts in Auckland and Wellington said they believed the true domestic violence victimisation rates were higher than the "moderate scenario" rates of 18.2 per cent for women and 1.9 per cent for men.
"We were struggling to find empirical evidence of an estimate that would be higher than 18.2 per cent," Ms Kahui said. "So it was about finding something higher."
Jeepers. Kudos to Ms. Kahui for pointing out that there was a quest to find a big number.

I note that Suzanne Snively also authored the PWC report on Adult and Continuing Education that estimated very large benefits from Adult and Continuing Education by assuming that anybody taking a night cooking course would be 50% less likely to commit any crime.

Congrats too to Simon Collins for catching this. I didn't have time to look through the report yesterday when I saw the big number floating around; nice to see that others have started sniffing out this stuff.