title: How important is selection? Experimental vs non-experimental measures of the income gains from migration

authors: McKenzie, David

subjects: migration

abstract: Measuring the gain in income from migration is complicated by non-random selection of migrants from the general population, making it hard to obtain an appropriate comparison group of non-migrants. This paper uses a migrant lottery to overcome this problem, providing an experimental measure of the income gains from migration. New Zealand allows a quota of Tongans to immigrate each year with a lottery used to choose amongst the excess number of applicants. A unique survey conducted by the authors in these two countries allows experimental estimates of the income gains from migration to be obtained by comparing the incomes of migrants to those who applied to migrate, but whose names were not drawn in the lottery, after allowing for the effect of non-compliance among some of those whose names were drawn. We also conducted a survey of individuals who did not apply for the lottery. Comparing this non-applicant group to the migrants enables assessment of the degree to which non-experimental methods can provide an unbiased estimate of the income gains from migration. We find evidence of migrants being positively selected in terms of both observed and unobserved skills. As a result, non-experimental methods are found to overstate the gains from migration, by 9 to 82 percent. A good instrumental variable works best, while difference-in-differences and bias-adjusted propensity-score matching also perform comparatively well.

text: How important is selection? Experimental vs non-experimental measures of the income gains from migration Measuring the gain in income from migration is complicated by non-random selection of migrants from the general population, making it hard to obtain an appropriate comparison group of non-migrants. This paper uses a migrant lottery to overcome this problem, providing an experimental measure of the income gains from migration. New Zealand allows a quota of Tongans to immigrate each year with a lottery used to choose amongst the excess number of applicants. A unique survey conducted by the authors in these two countries allows experimental estimates of the income gains from migration to be obtained by comparing the incomes of migrants to those who applied to migrate, but whose names were not drawn in the lottery, after allowing for the effect of non-compliance among some of those whose names were drawn. We also conducted a survey of individuals who did not apply for the lottery. Comparing this non-applicant group to the migrants enables assessment of the degree to which non-experimental methods can provide an unbiased estimate of the income gains from migration. We find evidence of migrants being positively selected in terms of both observed and unobserved skills. As a result, non-experimental methods are found to overstate the gains from migration, by 9 to 82 percent. A good instrumental variable works best, while difference-in-differences and bias-adjusted propensity-score matching also perform comparatively well.

year: 2006-03

title: Flow maldistribution in industrial air heaters and its effect on heat transfer

authors: Atkins, Martin John

abstract: Flow maldistribution in cross-flow heat exchangers used for industrial air heaters or recuperators is fairly common and can lead to a number of undesirable effects, one of which is deterioration in the thermal performance. The effect of gross flow maldistribution and the improvement in the thermal performance of flow correction guide vanes is investigated using a laboratory heat exchanger apparatus. The thermal performance deterioration from maldistribution was up to around 30 %. Modest improvements in the overall heat transfer coefficient and heat exchanger effectiveness when vanes were used was found for the range of air-side Reynolds numbers tested. Vanes were found to reduce the deterioration in thermal performance by up to 60 % compared to a perfectly uniform flow situation. Based on the ε-NTU correlations the thermal performance deterioration is predicted to decrease as the number of tube rows (i.e. NTU) increases. The effective heat transfer area and therefore thermal performance of industrial air heaters and recuperators can be improved by using flow correction devices, such as guide vanes.

text: Flow maldistribution in industrial air heaters and its effect on heat transfer Flow maldistribution in cross-flow heat exchangers used for industrial air heaters or recuperators is fairly common and can lead to a number of undesirable effects, one of which is deterioration in the thermal performance. The effect of gross flow maldistribution and the improvement in the thermal performance of flow correction guide vanes is investigated using a laboratory heat exchanger apparatus. The thermal performance deterioration from maldistribution was up to around 30 %. Modest improvements in the overall heat transfer coefficient and heat exchanger effectiveness when vanes were used was found for the range of air-side Reynolds numbers tested. Vanes were found to reduce the deterioration in thermal performance by up to 60 % compared to a perfectly uniform flow situation. Based on the ε-NTU correlations the thermal performance deterioration is predicted to decrease as the number of tube rows (i.e. NTU) increases. The effective heat transfer area and therefore thermal performance of industrial air heaters and recuperators can be improved by using flow correction devices, such as guide vanes.

year: 2014-08-31

title: Important lessons for trust governance from trusts that benefit New Zealand's Indigenous Maori – Recent developments

authors: Manyam, Joel

abstract: The landmark New Zealand Court of Appeal decision in New Zealand Maori Council v AttorneyGeneral [1987] 1 NZLR 641[SOE Case] marked a watershed in New Zealand's jurisprudence concerning the relationship between the Government of New Zealand('the Crown') and the indigenous Maori peoples of New Zealand. Very recently , New Zealand's highest Court, the Supreme Court in its decision in New Zealand Maori Council v Attorney-General[2013] 3 NZLR 31 referred to the SOE case as follows:
'The SOE case by the Court of Appeal is a judgment of great authority and importance to the law concerning the relationship between the Crown and Maori" (emphasis added)[S3].

text: Important lessons for trust governance from trusts that benefit New Zealand's Indigenous Maori – Recent developments The landmark New Zealand Court of Appeal decision in New Zealand Maori Council v AttorneyGeneral [1987] 1 NZLR 641[SOE Case] marked a watershed in New Zealand's jurisprudence concerning the relationship between the Government of New Zealand('the Crown') and the indigenous Maori peoples of New Zealand. Very recently , New Zealand's highest Court, the Supreme Court in its decision in New Zealand Maori Council v Attorney-General[2013] 3 NZLR 31 referred to the SOE case as follows:
'The SOE case by the Court of Appeal is a judgment of great authority and importance to the law concerning the relationship between the Crown and Maori" (emphasis added)[S3].

year: 2015