A copula-based approach to accommodate intra-household interaction in workers' daily maintenance activity stop generation modeling

A new stop frequency model was developed to predict the daily number of maintenance activity stops made by individual household heads during a typical weekday. This new model was based on the modification of a conventional multivariate ordered probit(MOP) model by maintaining the probit assumption for the marginal distributions while introducing nonnormal dependence among the error terms using copula functions. Therefore, the copulabased MOP model would relieve the restriction of imposing joint normality on the error terms in the conventional MOP model. The new MOP model would not only account for the intrahousehold interactions in stop-making decisions, but also allow the best functional form to be determined for representing dependencies among household heads. Using the New York Metropolitan Transportation Council’s 2010/2011 regional household travel survey data, the copula-based MOP model was employed to examine stop-making behavior for individual household heads residing in New York City and its adjacent counties in Mid-Hudson Valley and New Jersey. Empirical results provided useful insights into the observed effects of sociodemographics, land use density, transportation service, and work schedule together with potential unobserved common effects on the inter-relatedness of spousal stop-making decisions at the household level. The results show that the MOP model with a Clayton copula structure provides the best data fits and there is a very strong positive dependence among error terms of stop-making equations. Furthermore, the dependence among the maintenance activity propensities of household heads is asymmetric, with a stronger tendency of household heads to simultaneously have low maintenance activity levels than to simultaneously have high maintenance activity levels.

Factors influencing adoption of soil and water conservation practices in the northwest Ethiopian highlands

Soil erosion has long been a problem in the Ethiopian highlands in general and Dembecha district in particular. The objective of this study was to identify factors influencing adoption of soil and water conservation practices. Both quantitative and qualitative data were collected from primary and sec-ondary sources. The primary data were collected from respondent samples and key informants through interview and personal observation. The secondary data were collected from sources such as books, journals, statistical reports and official documents. A multistage sampling technique was applied to select sample households. Sample sizes of 150 households were selected using simple random sampling. Both descriptive statistics and a multivariate probit econometric model were employed to analyze the data. The model results revealed that the likelihood of decisions to adopt soil bund, stone bund, check dam and strip cropping were 74, 56, 29 and 56%respectively. The joint probability of adopting the selected soil and water conservation practices was 14.2%. The model results also confirmed that age, sex, education level, household size, livestock holding, land size, access to credit, access to extension service and training were significant factors that affected the adoption of soil and water conservation practices in the study area. Based on our findings, the study suggests that the government and stakeholders should focus on strengthening the provision of formal and non-formal training and facilitate an effective extension service.