Acta geneticae medicae et gemellologiae: twin research, 1988
Twinning rates were studied in Swedes, Åland Islanders, Finns, Germans, and Dutch during years of... more Twinning rates were studied in Swedes, Åland Islanders, Finns, Germans, and Dutch during years of starvation when death rates were two to three times higher than average. In contrast to the situation among some animals, this study suggests that nutrition above a certain threshold is unimportant for human reproduction, including twinning. The twinning rates for these different populations display marked temporal differences, but low values in the twinning rate are not consistently associated with periods of epidemics, famine, or similar nutritional stress. After years of privation and/or separation of spouses, a rapid “catch-up effect” can often be seen in the twinning rates, as well as marriage and birth rates. Psychoendocrine factors and interparental immunological conditions that may be involved in this phenomenon are discussed.
Fellman, J. On Lorenz curves generated by a given class of transfer policies. Statistics, Econometrics and Society: Essays in honour of Leif Nordberg. Red: Rune Höglund, Markus Jäntti och Gunnar Rosenqvist. Statistikcentralen Forskningsrapporter nr. 238 2003:27-40
Biometric Analysis of the Multiple Maternities in Finland, 1881—1990, and in Sweden since 1751
Human Biology, 2014
Hellin's law states that if the twinning rate is w, then the triplet rate is w2, the quad... more Hellin's law states that if the twinning rate is w, then the triplet rate is w2, the quadruplet rate is w3, and so forth. The opinion of today is that Hellin's law holds only approximately. In this study the inaccuracy of Hellin's law is studied and the discrepancies are explained mathematically. In our earlier studies we built linear models for the twinning rate. Because most of the mothers are younger than 40 years of age and because in this age interval the twinning rate depends linearly on age, linear regression methods have been applied. Hellin's law suggests using the square-root transformation of the triplet rate r. Statistical arguments speak in favor of using the arcsin square root of r transformation. We discuss both transformations. Despite the fact that Hellin's law is only approximate, the arcsin transformation proves valuable. The transformed triplet rate can be modeled in a way similar to the twinning rate. We consider secular data from Finland for 1881-1990 and from Sweden since 1751. Using Hellin's law, we compare the triplet rates and the twinning rates and study the time trends of the observed twinning and triplet rates. The data are standardized. Our theoretical results are applied to multiple maternity data for Finland. Using maternal age as the regressor, we build a linear model for the twinning rate and for the arcsin-transformed triplet rate. This analysis shows a decreasing linear time trend in the triplet series for the period 1881-1950 but not in the twinning series. The triplet rate has an increasing trend after 1960, which seems to be mainly caused by artificial induction of ovulation.
Aldur W. Eriksson, the noted twin scholar and human geneticist, passed away on Friday, April 3, 2... more Aldur W. Eriksson, the noted twin scholar and human geneticist, passed away on Friday, April 3, 2015, at the age of 88. He had a full, highly productive and accomplished life. He is survived by his wife Maj-Britt and their son Staffan and his family. His death leaves a void, not only among relatives and friends, but among the many who had known him and in the scientific community, particularly that of twin researchers worldwide.
Forsius H. & Eriksson, A. W. & Fellman, J. Pigmentation in Skolt Saamis (Lapps). Baltic Eye (2010), http://www.thebalticeye.com/101-FORSIUS.html
Let X be the pre- and Y be the post-transfer income. In earlier studies we have considered the cl... more Let X be the pre- and Y be the post-transfer income. In earlier studies we have considered the class of transfer policies where Y=h(X) is the post-transfer income and h(x) is non-negative, monotone increasing and continuous. We modify this class, allowing h(x) to be discontinuous. If h(x) is discontinuous, then it can have only a countable number of finite positive steps. If there exists an optimal policy which Lorenz dominates all policies in the class, then it must be continuous. We present necessary and sufficient conditions under which a given Lorenz curve L ¯(p) can be generated by a member of the class. These conditions are equivalent to the condition that the transformed variable stochastically dominates the initial variable.
Primary income data yields the most exact estimates of the Gini coefficient. Using Lorenz curves,... more Primary income data yields the most exact estimates of the Gini coefficient. Using Lorenz curves, the Gini coefficient is defined as the ratio of the area between the diagonal and the Lorenz curve and the area of the whole triangle under the diagonal. Various attempts have been made to obtain accurate estimates. The trapezium rule is simple, but yields a positive bias for the area under the Lorenz curve and, consequently, a negative bias for the Gini coefficient. Simpson´s rule is better fitted to the Lorenz curve, but this rule demands an even number of subintervals of the same length. Lagrange polynomials of second degree can be considered as a generalisation of Simpson´s rule because they do not demand equidistant points. If the subintervals are of the same length, the Lagrange polynomial method is identical with Simpson´s rule. In this study, we compare different methods. When we apply Simpson´s rule, we mainly consider Lorenz curves with deciles. In addition, we use the trapezium rule, Lagrange polynomials and generalizations of Golden´s method (2008). No method is uniformly optimal, but the trapezium rule is almost always inferior and Simpson´s rule is superior. Golden´s method is usually of medium quality.
There has been a large number of studies in which the scientists have built models for income dis... more There has been a large number of studies in which the scientists have built models for income distributions. As an alternative, some have built models for Lorenz curves. The step from Lorenz curve to distribution function is more difficult than the step from distribution function to Lorenz curve. There is a difference between advanced and simple Lorenz models. Advanced models with several parameters yield a better fit to data, but are difficult to connect to exact income distributions. Simple one-parameter models can more easily be associated with the corresponding income distribution, but when statistical analyses are performed the goodness of fit is often poor. In this study, simple models are considered and the results compared with results obtained by numerical methods without any assumptions concerning the Lorenz model.
Acta geneticae medicae et gemellologiae: twin research, 1988
Twinning rates were studied in Swedes, Åland Islanders, Finns, Germans, and Dutch during years of... more Twinning rates were studied in Swedes, Åland Islanders, Finns, Germans, and Dutch during years of starvation when death rates were two to three times higher than average. In contrast to the situation among some animals, this study suggests that nutrition above a certain threshold is unimportant for human reproduction, including twinning. The twinning rates for these different populations display marked temporal differences, but low values in the twinning rate are not consistently associated with periods of epidemics, famine, or similar nutritional stress. After years of privation and/or separation of spouses, a rapid “catch-up effect” can often be seen in the twinning rates, as well as marriage and birth rates. Psychoendocrine factors and interparental immunological conditions that may be involved in this phenomenon are discussed.
Fellman, J. On Lorenz curves generated by a given class of transfer policies. Statistics, Econometrics and Society: Essays in honour of Leif Nordberg. Red: Rune Höglund, Markus Jäntti och Gunnar Rosenqvist. Statistikcentralen Forskningsrapporter nr. 238 2003:27-40
Biometric Analysis of the Multiple Maternities in Finland, 1881—1990, and in Sweden since 1751
Human Biology, 2014
Hellin's law states that if the twinning rate is w, then the triplet rate is w2, the quad... more Hellin's law states that if the twinning rate is w, then the triplet rate is w2, the quadruplet rate is w3, and so forth. The opinion of today is that Hellin's law holds only approximately. In this study the inaccuracy of Hellin's law is studied and the discrepancies are explained mathematically. In our earlier studies we built linear models for the twinning rate. Because most of the mothers are younger than 40 years of age and because in this age interval the twinning rate depends linearly on age, linear regression methods have been applied. Hellin's law suggests using the square-root transformation of the triplet rate r. Statistical arguments speak in favor of using the arcsin square root of r transformation. We discuss both transformations. Despite the fact that Hellin's law is only approximate, the arcsin transformation proves valuable. The transformed triplet rate can be modeled in a way similar to the twinning rate. We consider secular data from Finland for 1881-1990 and from Sweden since 1751. Using Hellin's law, we compare the triplet rates and the twinning rates and study the time trends of the observed twinning and triplet rates. The data are standardized. Our theoretical results are applied to multiple maternity data for Finland. Using maternal age as the regressor, we build a linear model for the twinning rate and for the arcsin-transformed triplet rate. This analysis shows a decreasing linear time trend in the triplet series for the period 1881-1950 but not in the twinning series. The triplet rate has an increasing trend after 1960, which seems to be mainly caused by artificial induction of ovulation.
Aldur W. Eriksson, the noted twin scholar and human geneticist, passed away on Friday, April 3, 2... more Aldur W. Eriksson, the noted twin scholar and human geneticist, passed away on Friday, April 3, 2015, at the age of 88. He had a full, highly productive and accomplished life. He is survived by his wife Maj-Britt and their son Staffan and his family. His death leaves a void, not only among relatives and friends, but among the many who had known him and in the scientific community, particularly that of twin researchers worldwide.
Forsius H. & Eriksson, A. W. & Fellman, J. Pigmentation in Skolt Saamis (Lapps). Baltic Eye (2010), http://www.thebalticeye.com/101-FORSIUS.html
Let X be the pre- and Y be the post-transfer income. In earlier studies we have considered the cl... more Let X be the pre- and Y be the post-transfer income. In earlier studies we have considered the class of transfer policies where Y=h(X) is the post-transfer income and h(x) is non-negative, monotone increasing and continuous. We modify this class, allowing h(x) to be discontinuous. If h(x) is discontinuous, then it can have only a countable number of finite positive steps. If there exists an optimal policy which Lorenz dominates all policies in the class, then it must be continuous. We present necessary and sufficient conditions under which a given Lorenz curve L ¯(p) can be generated by a member of the class. These conditions are equivalent to the condition that the transformed variable stochastically dominates the initial variable.
Primary income data yields the most exact estimates of the Gini coefficient. Using Lorenz curves,... more Primary income data yields the most exact estimates of the Gini coefficient. Using Lorenz curves, the Gini coefficient is defined as the ratio of the area between the diagonal and the Lorenz curve and the area of the whole triangle under the diagonal. Various attempts have been made to obtain accurate estimates. The trapezium rule is simple, but yields a positive bias for the area under the Lorenz curve and, consequently, a negative bias for the Gini coefficient. Simpson´s rule is better fitted to the Lorenz curve, but this rule demands an even number of subintervals of the same length. Lagrange polynomials of second degree can be considered as a generalisation of Simpson´s rule because they do not demand equidistant points. If the subintervals are of the same length, the Lagrange polynomial method is identical with Simpson´s rule. In this study, we compare different methods. When we apply Simpson´s rule, we mainly consider Lorenz curves with deciles. In addition, we use the trapezium rule, Lagrange polynomials and generalizations of Golden´s method (2008). No method is uniformly optimal, but the trapezium rule is almost always inferior and Simpson´s rule is superior. Golden´s method is usually of medium quality.
There has been a large number of studies in which the scientists have built models for income dis... more There has been a large number of studies in which the scientists have built models for income distributions. As an alternative, some have built models for Lorenz curves. The step from Lorenz curve to distribution function is more difficult than the step from distribution function to Lorenz curve. There is a difference between advanced and simple Lorenz models. Advanced models with several parameters yield a better fit to data, but are difficult to connect to exact income distributions. Simple one-parameter models can more easily be associated with the corresponding income distribution, but when statistical analyses are performed the goodness of fit is often poor. In this study, simple models are considered and the results compared with results obtained by numerical methods without any assumptions concerning the Lorenz model.
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