Search

We propose novel quantile regression methods when the response is discrete and the data come from a longitudinal design. The approach is based on conditional mid-quantiles, which have good theoretical properties even in the presence of ties. Optimization of a ridge-type penalized objective function accommodates for the data dependence. We investigate the performance and pertinence of our methods in a simulation study and an original application to macroprudential policies use in more than one hundred countries over a period of seventeen years. [ABSTRACT FROM AUTHOR]

We derive a multivariate latent Markov model with number of latent states that can possibly change at each time point. We model both the manifest and latent distributions conditionally on explanatory variables. Bayesian inference is based on a transdimensional Markov Chain Monte Carlo approach, where Reversible Jump is separately performed for each time occasion. In a simulation study, we show how our approach can recover the true underlying sequence of latent states with high probability, and that it has lower bias than competitors. We conclude with an analysis of the well-being of 100 nations, as expressed by the dimensions of the Human Development Index, for six-time points spanning a period of 22 years. R code with an implementation is available as supplementary material, together with files for reproducing the data analysis. [ABSTRACT FROM AUTHOR]

The effect of four different irrigation levels on the marketable yield and economic return of summer-growth lettuce was evaluated during 2005 and 2006 in Eastern Sicily, Italy. The viability of deficit irrigation was evaluated by estimating optimum applied water levels. Actual evapotranspiration ([ET.sub.0]) was estimated by combining pan evaporation measures and the Penman-Monteith approach ([ET.sub.0-PM]). The highest marketable yield of lettuce was recorded for plots receiving 100% [ET.sub.0-PM]. For deficit irrigated plots, reductions in crop production were ascribed to a decrease in lettuce weight. Crop coefficients equal to 1 determined maximum crop production values. Crop water use efficiency was maximum at a 100% [ET.sub.0-PM] level of water applied, corresponding to yield of 0.3 t [ha.sup.-1] [mm.sup.-1]. Irrigation water use efficiency reached its maximum at a 40% [ET.sub.0-PM] level, with values of 0.54 and 0.44 t [ha.sup.-1] [mm.sup.-1] during 2005 and 2006, respectively. Water applied and marketable yield of lettuce showed a significant quadratic relationship. Cost functions had a quadratic form during 2005 and a linear form during 2006. In the land-limiting condition the optimal economic levels fit the agronomic ones well. In the water-limiting condition, ranges of water deficit of 15-44% and 74-94% were as profitable as full irrigation, thus contributing to appreciable water savings. DOI: 10.1061/(ASCE)0733-9437(2008)134:4(437) CE Database subject headings: Economic factors: Evapotranspiration; Irrigation scheduling: Water management; Crops; Italy.