Influence of the gregarious instinct and individuals’ behavior patterns on macro migrations: Simulation experiments

The objective of the model is to simulate the migrations of social groups over certain geographical regions, influenced by the gregarious effect and individual behavior patterns. The people move in search of better work opportunities and welfare. The model components are regions and individuals belonging to certain social groups. A region is characterized by more than 30 parameters, such as geographical data, actual population statistics, education facilities, and work opportunities. For the social groups, the parameters include the demographic and educational statistics. The simulated individuals attempt to optimize their welfare by moving over the model map. Spontaneous migration, without apparent goal, is also considered. The region parameters change owing to the number and the parameters of incoming individuals, which provides a dynamic and nonlinear feedback. The qualitative results reveal that the model never reaches a steady state and that the social groups remain in periodical movement. The simulations are agent-based. No differential equations (like in the System Dynamics approach) or any extant theory or mathematical model is used.     

Shadow employment in post-transition—Is informal employment a matter of choice or no choice in Poland?

According to a dualistic view, shadow employment may follow from two main labour market failures: (i) official market labour taxation distortions make it ineffective for some agents to engage in registered employment due to a tax wedge; or (ii) for some workers regular employment may be unattainable do to some high access costs or demand constraints, which results in seeking earning opportunities beyond the boundaries of the official labour market. Whereas in the first case revenues from unofficial employment should be higher than the corresponding official ones (tax evasion hypothesis), in the alternative explanation labour market tightness seems to be an underlying reason (market segmentation hypothesis).We use a unique data set from a survey on undeclared employment from Poland. Using propensity score matching and decomposition techniques we demonstrate that workers of shadow economy are characterised by slightly higher endowments, while their revenues are considerably lower than among matched official economy counterparts. Although unobservable heterogeneity is considerable, results are robust. Although this is not direct evidence, we believe these results point to the labour market segmentation hypothesis and endangerment with social exclusion.     

Estimation of the same parameters under different data

In the paper some problems of minimax estimation and prediction are solved in the case when statisticians estimate the same parameters (predict the values of random variables which distribution depends on the same parameters), know the dimensions of the samples of their colleagues but do not know the values of these samples     

The problem of two-group identification 2

The sample-based identification rules for the problem of two-group identification have been defined. The essentially complete class of tests was used to describe the essentially complete class of sample-based identification rules. In the problem of multinomial identification the minimal essentially complete class of sample-based rules was found and compared with the rules derived from density estimators.     

On some properties of the dual of a totally balanced block design

In this paper it is shown that the dual of a totally balanced block design with t = b, is also a totally balanced block design. It is shown that Fisher's inequality $\text{b≧t}$ for BIB designs, holds also for a totally balanced block design.