On the positive association of parliamentary social choice functions

Intuitively, a voting rule satisfies the condition of positive association if it guarantees that an improvement for an alternative in the preferences expressed by voters results in a change, if there is any, of the social status of that alternative in the same direction. In this article, we consider two interpretations of this notion, and for parliamentary voting procedures, we provide results showing under the impartial anonymous culture (IAC) hypothesis how often the positive association is (not) satisfied. Furthermore, our analysis also permits us to investigate the relationships between these notions.     

Are Condorcet procedures so bad according to the reinforcement axiom?

A Condorcet social choice procedure elects the candidate that beats every other candidate under simple majority when such a candidate exists. The reinforcement axiom roughly states that given two groups of individuals, if these two groups select the same alternative, then this alternative must also be selected by their union. Condorcet social choice procedures are known to violate this axiom. Our goal in this paper is to put this important voting theory result into perspective. We then proceed by evaluating how frequently this phenomenon is susceptible to occur.     

Statistical inference for the effect of magnetic brain stimulation on a motoneurone

A stochastic model is developed for the possible excitatory and inhibitory effects of a stimulus to the brain on the activity of single human motoneurones. The model consists of a Wiener process for the build-up of underlying potential, a deterministic effect due to the stimulus and a random lag from brain to muscle. Direct likelihood inference for its parameters seems impossible, and we study the use of simulation to estimate the log-likelihood for the parameters of substantive interest. Monte Carlo methods yield point and confidence interval estimates of the membrane excitability underlying excitatory and inhibitory effects. The main qualitative conclusion is that both excitatory and inhibitory effects are unambiguously present. The contribution of statistical analysis to this problem is to provide accurate and apparently reliable inference for the quantities of neurophysiological interest. More generally, our methodology has the potential to make accurate likelihood-based inferences in challenging problems, but the computational burden can be large, particularly if the model is not fully adequate for the data, as in our application.     

Does having children affect women’s entrepreneurship decision? Evidence from Nigeria

Review of Economics of the Household - This paper investigates the impact of fertility on women’s entrepreneurship decision in Nigeria, using the 2008 and 2013 cross-sectional Demographic...     

The reinforcement axiom under sequential positional rules

The reinforcement axiom roughly states that when an alternative is selected by two different constituencies, it must also be selected by their union. Hare and Coombs rules are special cases of sequential positional voting rules, which are known to violate this axiom. In this article, we first show that reinforcement can be violated by all such rules. We then evaluate, by the use of Monte Carlo simulations and the Fishburn–Gehrlein technique, the proportion of profiles at which this phenomenon occurs.     

The vulnerability of four social choice functions to coalitional manipulation of preferences

The vulnerability of a social choice function to coalitional manipulation of preferences is defined as the proportion of voting situations in which the social choice function can be manipulated by a coalition of individuals. In this paper, we provide exact relations giving the vulnerability of four specific social choice functions (plurality rule, anti-plurality rule, plurality with runoff, anti-plurality with runoff) in three-alternative elections. Plurality with runoff appears to be less vulnerable than the other three rules.     

Small-scale farming in semi-arid areas: Livelihood dynamics between 1997 and 2010 in Laikipia,Kenya

The rural population of semi-arid lands in Kenya face multiple challenges that result from population growth, poor markets, land use and climatic changes. In particular, subsistence oriented farmers face various risks and opportunities in their attempt to secure their livelihoods. This paper presents an analysis on how livelihood assets and strategies of smallholders in Laikipia County, Kenya, have changed within the last decade and discusses the implications for development interventions. The analysis is based on bi-temporal data from 170 semi-structured household interviews in 1997 and a follow-up survey of 30 households conducted in 2010. Well-being indicators were developed and livelihood portfolios compared. The results show a striking persistence in low asset endowment for the majority of smallholders from an aggregated perspective, whereas transitions into and out of better livelihood conditions become evident from a household perspective. The investment in, and accumulation of, conventional buffer or productive assets, such as grain stocks, livestock or land, does not shield households from adverse shocks and stresses as smallholders were shown to easily slip back into poverty. Household portfolios display particular constraints for smallholders in expanding natural resource related activities and a substantial decrease in livestock numbers. While off-farm activities could possibly increase well-being, the prevailing low income levels and high insecurity for the majority who are engaged in off-farm employment, limits the ability to increase livelihood assets in the area.     

On admissible strategies and manipulation of social choice procedures

A collective choice mechanism can be viewed as a game in normal form; in this article it is shown, for very attractive rules and for sets with any number of alternatives, how individuals involved in a collective decision problem can construct the preferences they choose to express. An example is given with a version of plurality rule. Manipulability results are deduced from such a characterization.