In this article, we study exponentially weighted moving average (EWMA) charts for monitoring Weibull quantiles (percentiles) based on a monitoring statistic conditioned on ancillary statistics when samples may be Type II censored. The monitoring statistic has a distribution form that is intractable, but analytic forms of the density and distribution functions can be derived when it is conditioned on ancillary statistics. We use these results to develop EWMA control charts and, in certain cases, evaluate their average run length without resorting to simulations. We compare the average run length performance of the EWMA charts with those of probability-limit charts, studied by the authors, and probability-limit charts enhanced with Western Electric alarm rules. We apply the charts to the breaking strength of carbon fibers to detect shifts in a specific Weibull quantile.

We construct a stochastic dynamic dual model to investigate the structural adjustment of two aggregate output and three aggregate input categories in US agriculture under stochastic climatic change. More than a century of national annual data (1910–2011) is used in the empirical analysis. No constraints on asset fixity are imposed. Results indicate that, with rational expectations, both output categories as well as all input categories exhibit quasi‐fixity in response to market change and stochastic climate change. Crops adjust more than twice as fast as livestock—49% versus 20% of the way toward their long‐run equilibrium in one year. Fertilizer adjusts most rapidly toward equilibrium levels (88% in one year), and capital adjusts most slowly (5% in one year). Labor oscillates rather than converging smoothly toward equilibrium; its distance from equilibrium is the same as if it adjusted 59% of the way toward its optimal level in one year. Failing to anticipate climate change dramatically slows the estimated rate of adjustment for two netputs and modestly speeds the rate for two others, thus likely increasing overall adjustment costs. Failing to account for uncertainty in anticipated climate change has little impact on adjustment rates.

Purpose The purpose of this paper is to investigate the impacts of China’s urban segregation caused by hukou restrictions on food consumption. Design/methodology/approach Based on the 2007–2009 Urban Household Survey data from six China provinces conducted by the National Bureau of Statistics of China, the authors adopt a propensity score matching (PSM) method to correct for potential selection bias. A Rosenbaum bounds test is applied to evaluate the sensitivity of the PSM results to unobserved variables. Findings The results show that holding rural hukou (RHs) reduces the consumption of livestock products and vegetables and fruit by 8.8 and 4.8 percent, respectively. The status of hukou does not affect the consumption of grain and edible oil. Hukou impacts on food consumption are heterogeneous across income levels, with low-income and middle-income households more vulnerable to urban segregation and hukou discriminations. A stronger motivation for precautionary saving and higher welfare expenditures that not compensated by social security lead to the lower food consumption by migrant households with RHs. Originality/value This paper advances the research frontier by investigating the impacts of hukou system on the structure of food consumption, which accurately reflects the household welfare.

PurposeThis paper aims to examine impacts of the poverty alleviation relocation (PAR) program on diet quality of low-income households in China. We explore the impact mechanism of relocation on diet quality and the heterogeneous effects of different relocation modes.Design/methodology/approachA fixed effects model is constructed using panel data of 1126 low-income households collected over three years in eight provinces of China. The PAR program provides a natural experiment which dramatically changes the living conditions surrounding farmers. We are able to identify the causal effects of relocation on diet quality free from selection bias.FindingsThe empirical results show that the PAR program improves diet quality of low-income households and that better market access and increasing incomes induced by relocation play an important role in this improvement. Improved market access significantly reduces the over-consumption of staple foods, whereas higher income significantly reduces the intake divergences of non-staple foods. The impacts of different relocation modes on diet quality are highly heterogeneous.Practical implicationsOur findings indicate that the PAR program benefits diet quality of low-income households through greater market access and increases in total household income. Market improvements and food subsidies are conducive to improving the diet quality of the low income.Originality/valueDespite widespread evidences of healthy diets being associated with household environments and income, selection bias remains. This paper utilizes an exogenous program to explore the causal impacts of market access and family income on diet quality and to separate their different effects.

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