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Below results based on the criteria 'duration'
Total number of records returned: 20

Cosponsorship Coalitions in the U.S. House of Representatives
Grant, J. Tobin
Pellegrini, Pasquale (Pat) A.

Uploaded 04-22-1998
Keywords clustering
duration models
hazard models
spatial models
Abstract urrent theories and methods for studying of cosponsorship assume that the decision to cosponsor is identical to decision to vote. In this paper we develop a new theory of cosponsorship that identifies where along the ideological spectrum cosponsors of a bill are more likely to be. Moreover, we predict that members with organizational ties to the sponsor are more likely to cosponsor than other members. To test this theory, we employ a spatial duration model. This method has recently been used by geographers to estimate areas that are more likely to experience an "event." Using this technique permits a statistical test that supports our substantive hypotheses that cosponsorship coalitions are shaped by the characteristics of the location of the bill, the shared ties to the sponsor, and the policy area. In addition, more active sponsors are associated with wider and less clustered coalitions. These findings demonstrate that theories of the voting decision are not applicable to cosponsorship.

Electoral Reform and Legislative Structure: The Effects of Australian Ballot Laws on House Committee Tenure
Katz, Jonathan
Sala, Brian R.

Uploaded 01-01-1995
Keywords congress
personal vote
australian ballot
duration model
Abstract Most scholars agree that members of Congress are strongly motivated by their desire for reelection. This assumption implies that MCs adopt institutions, rules and norms of behavior in part to serve their electoral interests. Direct tests of the electoral connection are rare, however, because significant, exogenous changes in the electoral environment are difficult to identify. In this paper, we develop and test an electoral rationale for the norm of committee tenure, in which returning MCs typically retain their same assignments. We examine tenure patterns before and after a major, exogenous change in the electoral system -- the states' rapid adoption of Australian Ballot laws in the early 1890s. The ballot changes, we argue, induced new ``personal vote'' electoral incentives, which contributed to the adoption of ``modern'' Congressional institutions such as ``property rights'' to committee assignments. We demonstrate that there was a marked increase in assignment stability after 1892, when a majority of states had put the new ballot laws into force -- earlier than previous studies have suggested.

Strategic Position-Taking and the Timing of Voting Decisions in Congress
Box-Steffensmeier, Janet M.
Zorn, Christopher
Arnold, Laura W.

Uploaded 01-01-1995
Keywords timing
Congressional voting
duration models
proportional hazards
survival rate
Abstract Voting behavior is intimately linked with many of the most prominent questions of concern to students of legislatures, including the strength of legislative parties and factions, the parameters of individual decision making, and the nature of representation (Collie 1985). One critical element of voting in legislatures is the timing of various choices legislators make. The study of strategic position taking and the timing of voting decisions is important for three major reasons: it adds information about the context and sequence of decision making; the analysis more closely approximates members' strategic considerations; and finally, in contrast to most of the literature on legislative roll call voting, the process is examined rather than strictly the result. Yet, despite the importance of position taking and timing, no one has examined comprehensively this crucial aspect of timing. Research on the timing of voting decisions provides insight into theoretical questions regarding the strategic behavior of legislators, institutional constraints on member behavior, and strategies of interest group influence. The project examines the vote to ratify the North American Free Trade Agreement, which has been called ". . . the most important vote on Capital Hill since the Berlin Wall came down" (Frenzel 1994, 3).

Getting the Mean Right: Generalized Additive Models
Beck, Nathaniel
Jackman, Simon

Uploaded 00-00-0000
Keywords non-parametric regression
non-linear egression
Monte Carlo analysis
interaction effects
cabinet duration
Abstract We examine the utility of the generalized additive model as an alternative to the common linear model. Generalized additive models are flexible in that they allow the effect of each independent variable to be modelled non-parametrically while requiring that the effect of all the independent variables is additive. GAMs are common in the statistics literature but are conspicuously absent in political science. The paper presents the basic features of the generalized additive model. Through Monte Carlo experimentation we show that there is little danger of the generalized additive model finding spurious structures. We use GAMS to reanalyze several political science data sets. These applications show that generalized additive models can be used to improve standard analyses by guiding researchers as to the parametric shape of response functions. The technique also provides interesting insights about data, particularly in terms of modelling interactions.

Modelling Space and Time: The Event History Approach
Beck, Nathaniel

Uploaded 08-22-1996
Keywords duration analysis
event history analysis
time-series--cross-section data
discrete duration data
duration dependence
Abstract This is an elementary exposition of duration modelling prepared for a volume in celebration of the 30th anniversary of the Essex Summer School (Research Strategies in the Social Sciences, Elinor Scarbrough and Eric Tanenbaum, editors). The approach is non-mathematical. The running example used is the King et al. model of cabinet durations with particular attention paid to detecting and interpreting duration dependence in that model. There is some new discussion of ascertaining duration dependence using discrete methods and the relationship between discrete duration data and binary time-series--cross-section data.

Beyond Ordinary Logit: Taking Time Seriously in Binary Time-Series--Cross-Section Models
Beck, Nathaniel
Katz, Jonathan
Tucker, Richard

Uploaded 08-22-1997
Keywords binary time-series--cross-section data
temporal dependence
grouped duration models
complementary log-log
cubic spline
economic interdependence
democratic peace
Abstract Researchers typically analyze time-series--cross-section data with a binary dependent variable (BTSCS) using ordinary logit or probit. However, BTSCS observations are likely to violate the independence assumption of the ordinary logit or probit statistical model. It is well known that if the observations are temporally related that the results of an ordinary logit or probit analysis may be misleading. In this paper, we provide a simple diagnostic for temporal dependence and a simple remedy. Our remedy is based on the idea that BTSCS data is identical to grouped duration data. This remedy does not require the BTSCS analyst to acquire any further methodological skills and it can be easily implemented in any standard statistical software package. While our approach is suitable for any type of BTSCS data, we provide examples and applications from the field of International Relations, where BTSCS data is frequently used. We use our methodology to re-assess Oneal and Russett's (1997) findings regarding the relationship between economic interdependence, democracy, and peace. Our analyses show that 1) their finding that economic interdependence is associated with peace is an artifact of their failure to account for temporal dependence and 2) their finding that democracy inhibits conflict is upheld even taking duration dependence into account.

Getting the Mean Right is a Good Thing: Generalized Additive Models
Beck, Nathaniel
Jackman, Simon

Uploaded 01-30-1997
Keywords non-parametric regression
scatterplot smoothing
local fitting
cabinet duration
democratic peace
Abstract This is a substantial revision of the paper submitted as beck96. A shorter version of this paper is under consideration at a political science journal of note. Theory: Social scientists almost always use statistical models positing the dependent variable as a linear function of X, despite suspicions that the social and political world is not so parsimonious. Generalized additive models (GAMs) permit each independent variable to be modelled non-parametrically while requiring that the independent variables combine additively, striking a sensible balance between the flexibility of non-parametric techniques and the ease of interpretation and familiarity of linear regression. GAMs thus offer social scientists a practical methodology for improving on the extant practice of ``linearity by default''. Method: We present the statistical concepts and tools underlying GAMs (e.g., scatterplot smoothing, non-parametrics more generally, and accompanying graphical methods), and summarize issues pertaining to estimation, inference, and the statistical properties of GAMs. Monte Carlo experiments assess the validity of tests of linearity accompanying GAMs. Re-analysis of published work in American politics, comparative politics, and international relations demonstrates the usefulness of GAMs in social science settings. Results: Our re-analyses of published work show that GAMs can extract substantive mileage beyond that yielded by linear regression, offering novel insights, particularly in terms of modelling interactions. The Monte Carlo experiments show there is little danger of GAMs spuriously finding non-linear structures. All data analysis, Monte Carlo experiments, and statistical graphs were generated using S-PLUS, Version 3.3. The routines and data are available at ftp://weber.uscd.edu/pub/nbeck/gam.

Unanticipated Delays: A Unified Model of Position Timing and Position Content
Boehmke, Frederick

Uploaded 12-09-2003
Keywords duration
discrete choice
seemingly unrelated
position taking
Abstract On potentially contentious votes or when the margin of an upcoming vote is expected to be small, public position announcements by elected representatives may be strategically linked to position content and ultimately, to vote choice. Strategic position timing may occur when legislators announce early in order to sway others' vote choice; it may occur late when legislators stall in order to gain more information or are hoping that a close margin will make their vote valuable to participants willing to make side payments. Since intentions behind delay may often be unobserved or even unobservable, existing empirical analyses are unable to capture them. In this paper I argue that unobserved factors that influence position timing are related to unobserved factors influencing position content. To test this prediction, I develop a seemingly unrelated discrete-choice duration model that estimates the relationship between unobserved factors in the two processes. I then estimate this model using data on position timing and position content from the vote for the North American Free Trade Agreement. The results provide clear evidence that the two processes are linked and are consistent with my arguments about the sources of unanticipated delay.

Covariate Functional Form in Cox Models
Keele, Luke

Uploaded 10-25-2005
Keywords Cox model
event history
survival models
duration models
Abstract In most event history models, the effect of a covariate on the hazard is assumed to have a log-linear functional form. For continuous covariates, this assumption is often violated as the effect is highly nonlinear. Assuming a log-linear functional form when the nonlinear form applies causes specification errors leading to erroneous statistical conclusions. Scholars can, instead of ignoring the presence of nonlinear effects, test for such nonlinearity and incorporate it into the model. I review methods to test for and model nonlinear functional forms for covariates in the Cox model. Testing for such nonlinear effects is important since such nonlinearity can appear as nonproportional hazards, but time varying terms will not correct the misspecification. I investigate the consequences of nonlinear function forms using data on international conflicts from 1950-1985. I demonstrate that the conclusions drawn from this data depend on fitting the correct functional form for the covariates.

Selection Bias and Continuous-Time Duration Models: Consequences and a Proposed Solution
Boehmke, Frederick
Morey, Daniel
Shannon, Megan

Uploaded 07-15-2003
Keywords duration
selection bias
monte carlo
Abstract In this paper we explore the consequences of non-random sample selection for continuous time duration analysis. While the consequences of selectivity are reasonably well-understood in linear regression and common discrete choice models, we have little or no understanding of how it affects duration models. In this paper we study this issue by conducting a series of Monte Carlo analyses that estimate common duration models on data that suffer from selectivity. Our findings indicate that the consequences are severe: both coefficients and standard errors may be biased in an unknown direction. In addition, we find that selection bias may create the appearance of (non-existent) duration dependence. Given these difficulties, we develop a solution for self-selectivity bias in duration models and present evidence that demonstrates its superiority to models that ignore the problem.

Modeling Sample Selection for Durations with Time-Varying Covariates
Boehmke, Frederick

Uploaded 07-02-2008
Keywords selection
selection bias
time-vary covariates
event history
exchange rates
Abstract We extend previous estimators for duration data that suffer from non-random sample selection to allow for time-varying covariates. Rather that a continuous-time duration model, we propose a discrete-time alternative that models the (constant) effects of sample selection at the time of selection across all years of the resulting spell. Properties of the estimator are compared to those of a naive discrete duration model through Monte Carlo analysis and indicate that our estimator outperforms the naive model when selection is non-trivial. We then apply this estimator to the question of the duration of monetary regimes.

Stochastic Dependence in Competing Risks
Gordon, Sanford C.

Uploaded 09-05-2001
Keywords Competing risks
duration models
survival models
event history
random effects
frailty models
unobserved heterogeneity
Monte Carlo simulation
legislative position-taking
cabinet survival
numeric integration
Markov Chain Monte Carlo
Abstract The term "Competing Risks" describes duration models in which spells may terminate via multiple outcomes: The term of a cabinet, for example, may end with or without an election; wars persist until the loss or victory of the aggressor. Analysts typically assume stochastic independence among risks, the duration modeling equivalent of independence of irrelevant alternatives. However, many political examples violate this assumption. I review competing risks as a latent variables approach. After discussing methods for modeling dependence that place restrictions on the nature of association, I introduce a parametric generalized dependent risks model in which inter-risk correlation may be estimated and its significance tested. The method employs risk-specific random effects drawn from a multivariate normal distribution. Estimation is conducted using numerical methods and/or Bayesian simulation. Monte Carlo simulation reveals desirable large sample properties of the estimator. Finally, I examine two applications using data on cabinet survival and legislative position taking.

A Copula Approach to the Problem of Selection Bias in Models of Government Survival
Chiba, Daina
Martin, Lanny
Stevenson, Randy

Uploaded 01-02-2014
Keywords selection bias
copula theory
duration models
government survival
government formation
Abstract Recent theories of coalition politics in parliamentary democracies suggest that government formation and survival are jointly determined outcomes. An important empirical implication of these theories is that the sample of observed governments analyzed in studies of government survival may be nonrandomly selected from the population of potential governments. This can lead to serious inferential problems. Unfortunately, current empirical models of government survival are unable to account for the possible biases arising from nonrandom selection. In this study, we use a copula-based framework to assess, and correct for, the dependence between the processes of government formation and survival. Our results suggest that existing studies of government survival, by ignoring the selection problem, significantly overstate the substantive importance of several covariates commonly included in empirical models.

Aggregation Among Binary, Count, and Duration Models
King, Gary
Signorino, Curtis S.
Alt, James E.

Uploaded 08-28-2000
Keywords Duration
event count
renewal process
Abstract Binary, count, and duration data all code discrete events occurring at points in time. Although a single data generation process can produce all of these three data types, the statistical literature is not very helpful in providing methods to estimate parameters of the same process from each. In fact, only a single theoretical process exists for which known statistical methods can estimate the same parameters --- and it is generally used only for count and duration data. The result is that seemingly trivial decisions about which level of data to use can have important consequences for substantive interpretations. We describe the theoretical event process for which results exist, based on time-independence. We also derive a set of models for a time-dependent process and compare their predictions to those of a commonly used model. Any hope of understanding and avoiding the more serious problems of aggregation bias in events data is contingent on first deriving a much wider arsenal of statistical models and theoretical processes that are not constrained by the particular forms of data that happen to be available. We discuss these issues and suggest an agenda for political methodologists interested in this very large class of aggregation problems.

A Frailty Model of Negatively Dependent Competing Risks
Gordon, Sanford C.

Uploaded 07-02-2000
Keywords duration
competing risks
cabinet survival
Abstract "Competing Risks" is a term used to describe duration models in which an individual spell may terminate via more than one outcome. Numerous applications in political science exist: For example, the term of a cabinet may end either with or without an election; criminal investigations may terminate either with prosecution or abandonment of a case; wars persist until the loss or victory of the aggressor state. Analysts typically assume stochastic independence among risks. However, many political examples are characterized by negative risk dependence: A high hazard rate for termination via one risk implies a low rate for termination via another. Ignoring this dependence can potentially bias inference. This paper suggests a class of bivariate (i.e. two risk), negatively dependent competing risks models. Negative risk dependence enters through an individual-specific random effect that simultaneously increases the hazard rate for one risk while decreasing the hazard for the second. Monte Carlo simulation reveals this specification to be superior to a naive model in which risks are assumed independent. Finally, I examine an application of the negative dependence model using Strom's (1985) and King et. al.'s (1990) data on cabinet survival.

Signals, Models, and Congressional Overrides of the Supreme Court
Zorn, Christopher
Hettinger, Virginia

Uploaded 04-05-1999
Keywords event history models
split-population duration models
Supreme Court
statutory decisions
Abstract Sparked by interest in game-theoretic representations of the separation of powers, empirical work examining congressional overrides of Supreme Court statutory decisions has burgeoned in recent years. Much of this work has been hampered, however, by the relative rarity of such events; as has long been noted, congressional attention to the Court is limited, and most Court decisions represent the last word on statutory interpretation. With this fact foremost in our minds, we examine empirically a number of theories regarding such reversals. We apply a split-population duration model to the survival of Supreme Court statutory interpretation decisions. This approach allows us to separate the factors which lead to the event itself (i.e., the presence or absence of an override in a particular case) from those which influence the timing of the event. We find that case-specific factors relating to the salience of a case are an important influence in the incidence of overrides, while Congress- and Court-specific political influences dominate the timing at which those overrides occur. By separating the incidence and timing of overrides, our results yield a more accurate and nuanced understanding of this aspect of the separation of powers system.

The In-and-Outers Revisited: Duration Analysis and Presidential Appointee Tenure
Tomlinson, Andrew R.
Anderson, William D.

Uploaded 11-09-1999
Keywords presidency
event history
competing risks
Abstract Much has been written about the "fraying" of the Presidential appointments system (NAPA, 1985), but little research has been conducted which takes advantage of recent advancements in event history modeling. The questions posed by many authors in this field focus on two variables -- the time someone spends in office (Joyce, 1990), and the reasons they give for leaving their job (Bonafede, 1987). Not only do event history models avoid the common pitfalls of using OLS to model temporal data (Box-Steffensmeier and Jones, 2000), but certain models allow the researcher to combine temporal data with categorical choice models. We run a simple version of a competing risks model to test the effects of theoretically-chosen covariates on the likelihood of presidential appointees leaving office at a given time. We find support for some hypotheses, specifically those dealing with stress related factors and financial pressures on staffer tenure.

Who Votes By Mail? A Dynamic Model of the Individual-Level Consequences of Vote-by-Mail Systems
Berinsky, Adam
Burns, Nancy
Traugott, Michael

Uploaded 04-17-1998
Keywords turnout
duration analysis
continuous-time multistate duration model
Abstract Throughout the years, a number of changes have been proposed to electoral laws with the aim of increasing voter turnout and altering the composition of the electorate to make it more reflective of the voting age population. The most recent of these innovations is voting-by-mail (VBM). While the use of VBM has spread through the United States, little empirical evaluation of the impact of VBM has been undertaken to date. The analysis presented here fills this gap in our knowledge by assessing the impact of VBM on the Oregon electorate through a multistate duration analysis (Heckman and Singer, 1984; Heckman and Walker, 1986, 1991) that takes into account other factors associated with election administration and characteristics of individual voters. This methodology has the added advantage of providing a reasonable basis for extrapolation of these effects to other jurisdictions. The results of our research suggest that VBM does increase voter turnout in the aggregate, although its effects are not uniform across all groups in the electorate. More importantly, it does not seem to exert any influence on the partisan composition of the electorate. From a methodological perspective, the use of a multistate duration analysis provides a promising approach to extrapolating the impact of a policy change from one jurisdiction to another when appropriate data are available in each.

Mandate Elections and Policy Change in Congress
Peterson, David A.M.
Stimson, James
Gangl, Amy E.
Grossback, Lawrence J.

Uploaded 04-20-1998
Keywords duration
discrete time
fractional polynomial
Abstract We postulate that members of Congress react to occasional elections which are unusual in outcome, unexpected, and carry a clear message about the direction of voter preferences. Our cases are 1964/65, 1980/81, and 1994/95. That reaction is movement in the direction of the perceived mandate, where both aggregate outcomes and individual behavior deviate from long-term norms under the temporary influence of perception of dramatic movements in voter preferences. We undertake analyses that show aggregate shifts in Congressional outcomes and individual departures from personal equilibria. We conclude with an event history analysis designed to capture the duration of this temporary phenomenon.

Proper Specification of Corrections for Non-proportional Hazards
Jin, Shuai
Boehmke, Frederick

Uploaded 07-16-2015
Keywords duration
proportional hazards
noproportional hazards
Cox model
Abstract Parametric and nonparametric duration models assume proportional hazards, which means the effect of a covariate on the hazard rate is constant over time. Researchers have developed techniques to test and correct non-proportional hazards. A common correction for non-proportional hazards is to interact the covariates with the natural logarithm of time. Including the interaction term with time means that the specification now involves time-varying covariates, and the model specification should reflect this feature. However, researchers often still treat these as models with only time-invariant covariates. Incorrect model specification results in biased estimates, especially for the covariates interacted with time. The direction of bias is not certain, but the incorrect models tend to overestimate the effects of these covariates. Model specification affects significance tests as well. This study examines 14 articles with corrections for non-proportional hazards, and concludes 6 of 8 use incorrect specifications, producing incorrect results.

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