This study aims to model Lee-Carter mortality with a Bayesian approach, where the parameters in the model are assumed to be random variables. The data used in this study is data on mortality rates by age group from the period 1950–2015. The sourced of data was from the UN website. Age groups are categorized by age 0 years, 1-5 years, 6-10 years, 11-15 years, ..., 86-90 years. The results of this study are from Bayes estimation obtained information that the average infant mortality rate (population aged less than one year) is high, then at the age of toddlers (1-4 years) average mortality rate decreases. Furthermore, the average mortality rate for children, adolescents, young and older people has increased again. Meanwhile, the relative speed of the pattern of changes in mortality at infant age (less than one year) is high enough. At the age of toddlers (1 – 4 years), the pattern of changes in mortality has increased. Then, in the population of the next age group until the older age group, the mortality continues to decrease. The pattern of changes in mortality is lowest in the elderly population.

This study aimed to model the smoothing of B-splines on the relationship between happiness and economic growth. The method used in this research is smoothing B-splines, which were in the process of determining knots and smoothing parameters (λ) based on the minimum GCV. The data used in the study came from Badan Pusat Statistik-Statistics Indonesia. The results of this study concluded that the smoothing of B-splines is quite good at modeling the relationship between the level of happiness (response variable) and economic growth (predictor variable). The smoothing B-splines model can explain the variation in the level of happiness by 71.583 percent.

The Zenga curve is a tool to measure income inequality that represents the income ratio between the bottom income group and the top income group. A proper Zenga curve is a Zenga curve that can detect variations in the Ratio. In this paper, we derive the functional form of the Zenga curve from Rohde's Lorenz curve model. The result of this paper is that the functional form of the Zenga curve from Rohde's version of the Lorenz curve model is a constant. It cannot represent the truly happening phenomenon of inequality.