Weibull Duration Model Research Articles

Modeling the Effects of Asphalt Overlay Design on Pavement Distress Initiation with Random Parameters Hazard-Based Duration Models

Pavement deterioration model is a key input to a pavement management system that optimizes pavement maintenance and rehabilitation (M&R) planning. As a typical pavement M&R technique, asphalt overlay is commonly implemented to restore pavement performance. However, the impact of its design factors on pavement deterioration is not well documented in existing publications. This study aimed to investigate the effects of asphalt overlay design on the initiation of various types of cracking and severe rutting with consideration of endogenous bias and unobserved heterogeneity. A series of random parameters Weibull duration models were developed based on 317 asphalt overlay projects, which were collected from the Long-Term Pavement Performance program. Endogenous overlay design, overlay thickness, milling indicator, and overlaid pavement deflection were identified to represent their heterogeneity caused by unobserved factors over highway sections. Based on analysis results, the endogenous overlay design was shown to underestimate the service life of overlaid pavement. The occurrence probability of overlaid pavement distress would significantly decrease with an increase of asphalt overlay thickness. The application of 30% reclaimed asphalt pavement materials would retard the occurrence of severe rutting, but accelerate the occurrence of all types of cracking. Relative to asphalt overlay, milling and overlay can significantly reduce the hazard rate of severe rutting and all types of cracking. In addition, existing pavement condition, overlaid pavement deflection, traffic volume, and climate factors were identified to have significant effects on the distress initiation in overlaid pavements.

A Duration Approach for Estimating the Marginal Renewal Cost at German Motorways

We estimate the marginal costs of road renewals as part of a social marginal cost scheme for road user charging. Within an analytical approach that mirrors the relationship between road deterioration, traffic load and road renewal, we use an accelerated failure time model for road pavement with the purpose to derive the effect from traffic increase on the length of road renewal cycles. Based on a comprehensive dataset for German motorways we fit a Weibull duration model with covariates such as traffic load from heavy vehicles as well as various control variables and derive the road deterioration elasticity with respect to heavy traffic. Similar to available studies for Sweden we find a deterioration elasticity below one, implying that Newbery’s (1985) fundamental theorem does not hold for the German motorway network. The shape parameter of the Weibull function indicates that there is an ageing or weathering effect, and higher traffic loads are not the sole factor impacting on shorter pavement lifetimes. Our estimations yield a marginal renewal cost, which makes up approximately 40% of the average renewal cost. It implies that road user charges based on marginal costs will not yield a sufficient revenue to cover total costs.

Global factors, uncertainty, weather conditions and energy prices: On the drivers of the duration of commodity price cycle phases

We investigate the role of global factors in explaining the length of commodity price cycle phases, using a continuous-time Weibull duration model and data for a panel of 33 countries over the period 1980Q1–2015Q4. We find evidence of increasing (constant) positive duration dependence for commodity price booms and busts (normal time spells). Global macroeconomic conditions - in particular, inflation, economic policy uncertainty and monetary policy actions - significantly affect the duration of all commodity price cycle phases. Global environmental conditions also impact the duration of commodity price booms, with a rise in average temperature (rainfall) increasing (reducing) their lengths. A larger number of military conflicts around the globe is associated with shorter booms and busts. Finally, we find that higher oil prices are linked with longer booms and shorter busts. • We investigate how global factors affect the length of commodity price cycle phases. • Global macroeconomic conditions significantly affect the duration of all phases. • Higher average temperature (rainfall) also increases (reduces) booms' duration. • A rise in military conflicts around the globe is linked with shorter booms/busts. • Higher oil prices are associated with longer (shorter) booms (busts).

ECONOMIC ACTIVITY, CREDIT MARKET CONDITIONS, AND THE HOUSING MARKET

In this paper, we assess the characteristics of the housing market and its main determinants. Using data for 20 industrial countries over the period 1970Q1–2012Q2 and a discrete-time Weibull duration model, we find that the likelihood of the end of a housing boom or a housing bust increases over time. Additionally, we show that the different phases of the housing market cycle are strongly dependent on the economic activity, but credit market conditions are particularly important in the case of housing booms. The empirical findings also indicate that although housing booms have similar lengths in European and non-European countries, housing busts are typically shorter in European countries. The use of a more flexible specification for the hazard function that is based on cubic splines suggests that it evolves in a nonlinear way. From a policy perspective, our study can be useful for predicting the timing and the length of housing boom–bust cycles. Moreover, it highlights the importance of monetary policy by influencing lending rates and affecting the likelihood of occurrence of housing booms.

Political leader survival: does competence matter?

We examine whether economic and military competence of political leaders affect their duration in office. We introduce leader heterogeneity in the selectorate theory of Bueno de Mesquita et al. (2003) and derive the hypothesis that in the presence of a revolutionary threat, economic competence is negatively related to political survival, but that the effect is moderated by the size of the winning coalition. As military and economic competence are negatively correlated, the opposite holds for military competence. We present empirical estimates using proxies for military and economic competence in a parametric Weibull duration model that support our theoretical predictions.

Count Distribution for Generalized Weibull Duration with Applications

An extension of the Poisson distribution is derived by considering a stochastic point process where the duration has a generalized Weibull distribution. This distribution is able to represent under, equi and over dispersion, a useful feature in data analysis. The computation of the probabilities and renewal function (expected number of renewals) are examined. Parameter estimation by the method of maximum likelihood is considered with applications of the count distribution to real frequency count data exhibiting under and over dispersion. It is shown that the generalized Weibull count distribution fits much better than the Weibull and gamma duration models.

Booms, Busts, and Normal Times in the Housing Market

We assess the existence of duration dependence in the likelihood of an end in housing booms, busts, and normal times. Using data for 20 industrial countries and a continuous-time Weibull duration model, we find evidence of positive duration dependence suggesting that housing market cycles have become longer over the last decades. Then, we extend the baseline Weibull model and allow for the presence of a change-point in the duration dependence parameter. We show that positive duration dependence is present in booms and busts that last less than 26 quarters, but that does not seem to be the case for longer phases of the housing market cycle. For normal times, no evidence of change-points is found. Finally, the empirical findings uncover positive duration dependence in housing market booms of European and non-European countries and housing busts of European countries. In addition, they reveal that while housing booms have similar length in European and non-European countries, housing busts are typically shorter in European countries.

The social status of migrants in Turkey

Purpose – The purpose of this paper is to investigate the social status of migrants in a culturally liberal and historically cosmopolitan port city in Turkey. Design/methodology/approach – A novel data set from the Izmir Labor Market Household Survey is used. Social status is measured by occupational status, wages, and education. In addition, parents’ education, as well as, duration of unemployment for migrants is analyzed. Occupational status and education analyzes are based on ordered probit models. The probability that an individual with given characteristics will have an uneducated parent is estimated with a probit model. Weibull duration model is employed for the unemployment duration. Findings – Migrants in Izmir are likely to have occupations that claim a lower status. Migrants have higher wages so migrants are taking jobs of lower status but higher pay. The probability of exiting unemployment for migrants is higher, that is the duration of unemployment for migrants is shorter. Male have higher edu...

Patient Loyalty in a Mature IDS Market: Is Population Health Management Worth It?

To understand patient loyalty to providers over time, informing effective population health management. Patient care-seeking patterns over a 6-year timeframe in Minnesota, where care systems have a significant portion of their revenue generated by shared-saving contracts with public and private payers. Weibull duration and probit models were used to examine patterns of patient attribution to a care system and the continuity of patient affiliation with a care system. Clustering of errors within family unit was used to account for within-family correlation in unobserved characteristics that affect patient loyalty. The payer provided data from health plan administrative files, matched to U.S. Census-based characteristics of the patient's neighborhood. Patients were retrospectively attributed to health care systems based on patterns of primary care. I find significant patient loyalty, with past loyalty a very strong predictor of future relationship. Relationships were shorter when the patient's health status was complex and when the patient's care system was smaller. Population health management can be beneficial to the care system making this investment, particularly for patients exhibiting prior continuity in care system choice. The results suggest that co-located primary and specialty services are important in maintaining primary care loyalty.

Testing for unobserved heterogeneity in exponential and Weibull duration models

We examine the use of the likelihood ratio (LR) statistic to test for unobserved heterogeneity in duration models, based on mixtures of exponential or Weibull distributions. We consider both the uncensored and censored duration cases. The asymptotic null distribution of the LR test statistic is not the standard chi-square, as the standard regularity conditions do not hold. Instead, there is a nuisance parameter identified only under the alternative, and a null parameter value on the boundary of the parameter space, as in Cho and White (2007a). We accommodate these and provide methods delivering consistent asymptotic critical values. We conduct a number of Monte Carlo simulations, comparing the level and power of the LR test statistic to an information matrix (IM) test due to Chesher (1984) and Lagrange multiplier (LM) tests of Kiefer (1985) and Sharma (1987). Our simulations show that the LR test statistic generally outperforms the IM and LM tests. We also revisit the work of van den Berg and Ridder (1998) on unemployment durations and of Ghysels et al. (2004) on interarrival times between stock trades, and, as it turns out, affirm their original informal inferences.

The Duration of Business Cycle Expansions and Contractions: Are There Change-Points in Duration Dependence?

The issue of whether the likelihood of an expansion or contraction ending is dependent on its age, i.e whether they are duration dependent, is widely addressed in the business cycles literature and evidence of positive duration dependence is found in several studies. However, there is an important issue that has not been explored in this literature yet: the presence of change-points in duration dependence. All the studies in this field depart from the assumption that the magnitude of duration dependence is the same over time. However, we conjecture that the degree of likeliness of an expansion or contraction ending as it gets older might change after a specific duration. To test for that possibility, this paper will allow for the presence of a change-point in the analysis of the duration of expansions and contractions for a group of 13 European and Non-European industrial countries over the period 1948-2009.The evidence provided by the estimation of a continuous-time Weibull duration model shows strong support for the presence of positive duration dependence, which is stronger for contractions than for expansions. Results also show that contractions have become longer over time and that their length is negatively affected by the length of the previous expansion. Most importantly, this paper provides quite interesting evidence for the presence of a change-point in duration dependence for expansions, but not for contractions. Results show that the magnitude of the duration dependence parameter decreases significantly when an expansion surpasses 10 years of duration. In particular, evidence of positive duration dependence is no longer found when an expansion surpasses that threshold.

Non-constant hazard function and inflation dynamics

This paper explores implications of nominal rigidity characterized by a non-constant hazard function for aggregate dynamics. I derive the NKPC under an arbitrary hazard function and parameterize it with the Weibull duration model. The resulting Phillips curve involves lagged inflation and lagged expectations. It nests the Calvo NKPC as a limiting case in the sense that the effects of both terms are canceled out under the constant-hazard assumption. Furthermore, I find lagged inflation always has negative coefficients, thereby making it impossible to interpret inflation persistence as intrinsic. The numerical evaluation shows that the increasing hazard function leads to hump-shaped impulse responses of in‡ation to monetary shocks, and output leads inflation.

Does Third-Party Enforcement or Domestic Institutions Promote Enduring Peace After Civil Wars? Policy Lessons From an Empirical Test

What causes peaceful resolution of civil wars to endure rather than to collapse into renewed fighting? Existing studies predict that third-party peace enforcement by the United Nations (UN) or domestic institutions such as democracy, parliamentary, and presidential institutions and the proportional representation (PR) electoral system promotes enduring peace in societies that have emerged from a civil war. However, extant empirical works test the effect of third-party enforcement but not the impact of domestic institutions on peace after civil wars. Hence, I test the impact of democracy, presidential, and parliamentary institutions, electoral systems—PR and majoritarian—and third-party enforcement by the UN on the durability of peace after termination of civil wars. Results from a bootstrapped Weibull duration model show that democracy and the PR electoral system significantly reduces the likelihood that civil war may recur, but that third-party enforcement by the UN does not have a significant effect on the hazard rate of peace spells. A brief case study analysis of recent attempts to build democratic institutions in Cambodia and Kosovo by the international community also supports the claims posited in this article.

Conditional Moment Tests for Parametric Duration Models

This paper develops and compares specification tests for parametric duration models estimated with censored data. The tests are based on generalized residuals (the integrated hazard), which is exponentially distributed if the model is correctly specified. I present several conditional moment tests based on the generalized residuals: a raw moments test, a test based on Laguerre polynomials, and a Lagrange multiplier (LM) test. The LM test extends Lancaster’s (1985) test by allowing an arbitrarily precise approximation of the likelihood under the alternative. The raw moments test implemented via an auxiliary regression is examined using both asymptotic and bootstrap critical values. Monte Carlo evidence indicates that no one test dominates the others in all situations in terms of size, power, and ease of use. When the data are not censored, the Laguerre test appears to be the best choice. When there is censoring in the data, the Laguerre test is still at least as powerful as the other tests, but the raw moment test may be more convenient to perform. For the convenience of the practitioner the explicit forms of the tests for exponential and Weibull duration models are presented.

The Impact of Range Pricing on Marketing Time and Transaction Price: A Better Mousetrap for the Existing Home Market?

In various markets around the country, some real estate professionals are employing a new pricing strategy that involves marketing homes for sale with a price range rather than a single asking price. This strategy is often touted as a mechanism that will attract more potential buyers to look at a house and thus result in reduced marketing times for existing homes, with prices determined by competitive forces. The purpose of this study is to empirically examine whether houses using range pricing, often referred to as value range marketing, sell in the same amount of time and sell for similar prices as those marketed in the traditional manner. Two staged least squares with a correction for sample selection and Weibull duration models are used to test the hypotheses, employing a sample of 5,852 residential houses that were sold during the period January 1999 to December 2000. In contrast to claims of the strategy’s proponents, the results indicate that houses take longer to sell when using the range pricing strategy after controlling for physical characteristics and market conditions. Furthermore, there is no evidence that this strategy has any significant impact on transaction prices.

Neighborhood characteristics and the targeting of tax increment financing in Chicago

Tax increment financing (TIF) is a local economic development tool that funds improvements in an area designated as a TIF district with property tax revenues generated from the growth in property values in the district. This paper tests a number of explanations for the location of TIF districts within a city by estimating Weibull duration models of the time to inclusion in a TIF district for neighborhoods in Chicago. The results suggest that a neighborhood's hazard of inclusion in a TIF district is positively related to neighborhood distress, the presence of Empowerment Zones, and the passage of time and negatively related to a neighborhood's political influence.

The Costs and Outcomes of Chiropractic and Physician Care for Workers' Compensation Back Claims

INTRODUCTION Recent studies suggest that both chiropractors and physicians provide effective care for back pain, but the relative costs of chiropractic and physician care are still debated (USDHHS, 1994). Manga et al. (1993) argue that chiropractors are less costly than physicians. Carey et al. (1995) use data on charges to conclude that primary care physicians are the least-cost providers. The relative costs of health care are not, however, the appropriate comparison for work-related back pain. Workers' compensation insurers and self-insured employers pay health-care costs and disability benefits for persons with work-related injuries. From the payers' viewpoint, relatively costly modes of health care are efficient if the care produces sufficiently large savings in indemnity benefits by reducing durations of work absences. The authors use data from a workers' compensation insurer (the Zenith Insurance Co.) to compare the sum of health care and indemnity costs for non-surgical back patients treated by chiropractors or physicians. The data refer to approximately 850 closed claims for episodes of back pain that began and ended between 1991 and 1993. The comparison groups are (1) cases treated by a physician but not by a chiropractor and (2) cases treated by a chiropractor but not by a physician. The authors' measures of health-care costs are payments to providers, rather than health-care charges. Charges are deceptive because payment discounts vary among providers. The authors compare chiropractors' and physicians' pricing, service mix, and service utilization, and describe how each contributes to the differences between the average health-care costs of claimants treated by chiropractors and physicians. The measures of outcomes are the distribution of injured workers among claim types (medical only, temporary disability only, and permanent partial disability) and the durations of temporary disability claims. The authors estimate an ordered logit model to determine the relative effect of chiropractic treatment on the distribution of claim types, controlling for differences between the characteristics of chiropractic and physician patients. The authors estimate a Weibull duration model to determine the relative effect of chiropractic treatment on durations of work absence within the temporary and permanent disability groups. One limitation of the study is that severity of injury is unobserved. The problem of unobserved differences between chiropractor and physician patients is addressed by estimating a second set of models in which support points are added to control for the effects of unobserved worker heterogeneity. To the authors' knowledge, this is the first application of the method to the problem of unobserved differences that can include the severity of health conditions. The cost data are unusual because they include both payments for health care and disability benefit payments. The results show that the average total costs of back claims treated by chiropractors are lower than the average total costs of back claims treated by physicians. Part of the cost differential reflects the fact that a relatively large proportion of chiropractic patients are not paid disability benefits because they return to work within California's three-day waiting period. This result is similar to Ebrall's (1992) findings for Australian workers. The apparent superiority of chiropractic care disappears, however, when the probability of returning to work in less than four days is estimated from multivariate models that control for unobserved heterogeneity in the characteristics of individual workers. These results show no significant differences in the effectiveness of chiropractic and physician care in determining the probability of returning to work within the waiting period. The estimates of the effects of care on durations of work absence for temporary and permanent disability claims do, however, weakly support the conclusion that chiropractors are more effective than physicians in reducing durations of work absence. …

Fitting Weibull duration models with random effects.

Duration time models often should include correlated failure times, due to clustered data. These random effects hierarchical models sometimes are called "frailty models" when used for survival analyses. The data analyzed here involve such correlations because patient level outcomes (the times until graft failure following kidney transplantation) are observed, but patients are clustered in different transplant centers. We describe fitting such models by combining two kinds of software, one for parametric survival regression models, and the other for doing Poisson regression in a hierarchical setting. The latter is implemented by using PRIMM (Poisson Regression and Interactive Multilevel Modeling) methods and software (Christiansen & Morris, 1994a). An illustrative example for profiling data is included with k = 11 kidney transplant centers and N = 412 patients.

An Estimation of the Hazard Rate of Firms Under Chapter 11 Protection

The instantaneous probability (hazard rate) of a firm's exit from Chapter 11 protection is examined. Using the Weibull duration model, the effect of various regressors and the effect of the time a firm spends under Chapter 11 protection on this instantaneous probability is analyzed. I show that the hazard increases significantly under Chapter 11. Among the variables chosen, the interest burden of the firm and the capacity utilization of the firm's industry significantly increase the hazard. Other firm-specific variables like the long-term debt-to-assets ratio and the number of shares outstanding and economy wide variables, like the prime interest rate and the gross national product growth rate have no significant effect on the hazard. Copyright 1994 by MIT Press.

Statistical analysis of commuters' route, mode, and departure time flexibility

This paper studies the effects of traffic information on Seattle-area commuters. Models of commuters' route-change frequency, the duration of traffic delay needed to induce a route change, and the influence of pre-trip traffic information on departure-time choice, mode choice, and route choice are estimated. Two modeling techniques are used in these estimations: an ordered logit probability approach and a Weibull duration model with a heterogeneity correction term. The findings of these model estimations provide important insights into how traveler information systems should be designed, implemented, and marketed.