Department of Economics / Institutionen för nationalekonomi med statistik

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A CUSUM PROCEDURE FOR DETECTION OF OUTBREAKS IN POISSON DISTRIBUTED MEDICAL HEALTH EVENTS
(University of Gothenburg, 2010-11-02) Jonsson, Robert
CUSUM procedures which are based on standardized statistics are often supposed to have expectation zero and being normally distributed. If these conditions are not satisfied it can have serious consequences on the determination of proper alarming bounds and on the frequency of false alarms. Here a CUSUM method for detecting outbreaks in health events is presented when the latter are Poisson distributed. It is based on a standardized statistic with a bias from zero that can be neglected. The alarming boundaries are determined from the actual distribution of the statistic rather than on normality assumptions. The boundaries are also determined from requirements on the probability of false alarms instead of the common practice to focus on average run lengths (ARLs). The new method is compared with other CUSUM methods in Monte Carlo simulations. It is found that the new method has about the same expected time to first motivated alarm and the same sensitivity. However, the new method has expected times to first false alarm that are 9 % – 90 % longer. The new method is applied to outbreaks of sick-listening and to outbreaks of Chlamydial infection.
A comparison of conditioned versus unconditioned forecasts of the V AR(l) process
(University of Gothenburg, 2003-05-01) Holgersson, Thomas; Lindström, Fredrik
The properties of a forecast usually depend upon whether the forecast is conditioned on the final period observation or not. In the case of unconditioned forecasts it is well known that the point predictions are unbiased. If on the other hand the forecast is conditional, then the forecast may be biased. Existing analytical results in literature are insufficient for describing the properties of the conditioned forecast properly, particularly in multivariate models. This paper examines some finite sample properties of conditioned forecasts of the VAR(l) process by means of Monte Carlo experiments. We use a number of parameter settings for the V AR( 1) process to demonstrate that the forecast bias of the conditioned forecast may be considerable. Hence, unless the analyst has a clear idea of whether the conditioned or unconditioned forecast is relevant for the time series being analysed, statistical inferences may be seriously erratic.
A COMPARISON OF TWO DESIGNS FOR ESTIMATING A SECOND ORDER SURFACE WITH A KNOWN MAXIMUM
(University of Gothenburg, 1994-04-01) Ekman, Claes
Two level fractional factorial designs with a star are often used when working with lower polynomial models. In this paper an alternative design is discussed and compared with the fractional factorial design. We are working under the assumption that the true underlying model is of second order with a known maximum point.
A Dual Approach to the Derivation of Feedback Demand Functions for Capital-Accumulating Agents
(University of Gothenburg, 2024-05) Bolin, Kristian; Caputo, Michael R.; Department of Economics
An optimal control model of a consumer is developed that accounts for the consumption of many goods and services, the accumulation of wealth, a state variable that affects instantaneous preferences and wealth accumulation, and contains several canonical models as special cases. Formulas are provided for the feedback consumption functions in terms of certain partial derivatives of a consumer’s lifetime indirect utility function, thereby obviating the need to solve the necessary conditions of Pontryagin or the Hamilton-Jacobi-Bellman equation. The intrinsic qualitative properties of the optimal control model in differential form are derived, and an example of how to implement the results for econometric purposes is provided as well.
A Dynamic Model of Inflation for Kenya 1974 - 1996
(1998) S. Ndungu, Njuguna; Durevall, Dick; Department of Economics
This paper develops an error correction model with the aim of analysing the behaviour of prices in Kenya during 1974 -1996. In estimating the model, we first test for cointegration in the money and foreign exchange markets, using the Johansen procedure. The cointegrating vectors are then included in an autoregressive distributed-lag model, and a general-to-specific procedure is applied to obtain a parsimonious, empirically constant, error correction model. We find that in the long run inflation emanates from movements in the exchange rate, foreign prices, and terms of trade. The error correction term for the monetary sector does not enter the model, but money supply and the interest rate influence inflation in the short run. Inflation inertia is found to be an important determinant of inflation up until 1993, when about 40% of the current inflation is carried over to the next quarter. After 1993, inertia drops to about 10%. The dynamics of inflation are also influenced by food supply constraints, proxied by maize-price inflation. These findings indicate that the exchange rate is likely to be a more efficient nominal anchor than money supply, and that inflation could be made more stable by policies that secure the supply of maize during droughts.
A Fair Share : Burden-Sharing Preferences in the United States and China
(2010-10) Fredrik Carlsson; Mitesh Kataria; Alan Krupnick; Elina Lampi; Åsa Löfgren; Ping Qin; Thomas Sterner; Susie Chung
Using a choice experiment, we investigated preferences for distributing the economic burden of decreasing CO2 emissions in the two largest CO2-emitting countries: the United States and China. We asked respondents about their preferences for four burden-sharing rules to reduce CO2 emissions according to their country’s 1) historical emissions, 2) income level, 3) equal right to emit per person, and 4) current emissions. We found that U.S. respondents preferred the rule based on current emissions, while the equal right to emit rule was clearly least preferred. The Chinese respondents, on the other hand, preferred the historical rule, while the current emissions rule was the least preferred. Respondents overall favored the rule that was least costly for their country. These marked differences may explain the difficulties countries face in agreeing how to share costs, presenting a tough hurdle to overcome in future negotiations. We also found that the strength of the preferences was much stronger in China, suggesting that how mitigation costs are shared across countries is more important there.
A Jury of Her Peers: The Impact of the First Female Jurors on Criminal Convictions
(2016-02) Anwar, Shamena; Bayer, Patrick; Hjalmarsson, Randi; Dept. of Economics, University of Gothenburg
This paper uses an original data set of more than 3000 cases from 1918 to 1926 in the Central Criminal Courts of London to study the effect of the Sex Disqualification (Removal) Act of 1919. Implemented in 1921, this Act made females eligible to serve on English juries, providing a novel setting for studying the impact of female representation on jury verdicts. Results based on a pre-post research design imply that the inclusion of females had little effect on overall conviction rates but resulted in a large and significant increase in convictions for sex offenses and on the conviction rate differential between violent crime cases with female versus male victims. The inclusion of women also increased the likelihood of juries being discharged without reaching a verdict on all charges and the average time taken to reach a verdict. A complementary analysis of cases in which the jury was carried over from a previous trial also implies that the inclusion of female jurors on the seated jury sharply increased conviction rates for violent crimes against women versus men.
A man´s world? – The impact of a male dominated environment on female leadership
(University of Gothenburg, 2018-11) Born, Andreas; Ranehill, Eva; Sandberg, Anna; Dept. of Economics, University of Gothenburg
Despite the significant growth in female labor force participation and educational attainment over the past decades, few women reach leadership positions. In this study, we explore whether male dominated environments, in and of themselves, adversely affect women´s willingness to lead a team. We find that women randomly assigned to male majority teams are less willing to become team leaders than women assigned to female majority teams. Analyses of potential mechanisms show that women in male majority teams are less confident in their relative performance, less influential, and more swayed by others in team discussions. They also (accurately) believe that they will receive less support from team members in a leadership election. Taken together, our results indicate that the absence of women in male dominated contexts may be a self-reinforcing process.
A Markov Chain Model for Analysing theProgression of Patient´sHealth States
(2011) Jonsson, Robert
Markov chains (MCs) have been used to study how the health states of patients are progressing in time. With few exceptions the studies have been based on the questionable assumptions that the MC has order m=1 and is homogeneous in time. In this paper a three-state non-homogeneous MC model is introduced that allows m to vary. It is demonstrated how wrong assumptions about homogeneity and about the value of m can invalidate predictions of future health states. This can in turn seriously bias a cost-benefit analysis when costs are attached to the predicted outcomes. The present paper only considers problems connected with model construction and estimation. Problems of testing for a proper value of m and of homogeneity is treated in a subsequent paper. Data of work resumption among sick-listed women and men are used to illustrate the theory. A nonhomogeneous MC with m = 2 was well fitted to data for both sexes. The essential difference between the rehabilitation processes for the two sexes was that men had a higher chance to move from the intermediate health state to the state ‘healthy’, while women tended to remain in the intermediate state for a longer time.
A Markov Copula Model of Portfolio Credit Risk with Stochastic Intensities and Random Recoveries
(2012-10) Bielecki, Tomasz R.; Cousin, Areski; Crépey, Stéphane; Herbertsson, Alexander; Dept of Economics, University of Gothenburg
In [4], the authors introduced a Markov copula model of portfolio credit risk. This model solves the top-down versus bottom-up puzzle in achieving efficient joint calibration to single-name CDS and to multi-name CDO tranches data. In [4], we studied a general model, that allows for stochastic default intensities and for random recoveries, and we conducted empirical study of our model using both deterministic and stochastic default intensities, as well as deterministic and random recoveries only. Since, in case of some “badly behaved” data sets a satisfactory calibration accuracy can only be achieved through the use of random recoveries, and, since for important applications, such as CVA computations for credit derivatives, the use of stochastic intensities is advocated by practitioners, efficient implementation of our model that would account for these two issues is very important. However, the details behind the implementation of the loss distribution in the case with random recoveries were not provided in [4]. Neither were the details on the stochastic default intensities given there. This paper is thus a complement to [4], with a focus on a detailed description of the methodology that we used so to implement these two model features: random recoveries and stochastic intensities.
A Microeconomic Analysis of Institutions
(2000) Olsson, Ola; Department of Economics
This survey paper has three themes; a microeconomic analysis of institutions, an institutional analysis of microeconomics, and a discussion on the scope for an "institutional microeconomics" that takes insights from psychology and older institutional theory into account. Institutions are defined as the long-run rules of the economy that have the character of public goods and whose main function is the reduction of transaction costs. The institutional requirements for the Walrasian equilibrium and for a cooperative solution in a Prisoner's Dilemma-like game, are thoroughly analyzed. The paper briefly surveys the main results from the OIE and NIE-schools and discusses the possibilities of an interdisciplinarily oriented institutional microeconomics.
A monitoring system for detecting starts and declines of influenza epidemics
(2003-12-01) Andersson, Eva
The aim is to detect an influenza outbreak as soon as possible. Data are weekly reports of number of patients showing influenza-like symptoms. At each additional observation we decide whether a change has occurred or not. The methodology of statistical surveillance is used to construct an outbreak detection system. The report also demonstrates measures that reflect timeliness, such as the probability of successful detection within a specified time and the predictive value at different time points. A new non-parametric approach is used. The cycles are estimated using only monotonicity restrictions. Also different approaches regarding the intensity of the change-process are compared. The pros and cons of using an empirical intensity are evaluated. The time to an alarm is investigated, both for false and motivated alarms. When setting the alarm limit, there is a trade-off between the false alarms and the delay of motivated alarms. In the evaluation it must be considered that the performance of the system depends on when the outbreak begins, in relation to the start of the surveillance. If the outbreak begins at the same time as the surveillance is started, then the probability of early detection is 0.04, but if the surveillance is started 12 time points before the outbreak the detection probability is 0.43. The non-parametric approach avoids miss-specifications of the base line. Even a "normal" miss-specification results in serious delay. Another drawback is that alarms at late time points have low predictive value. An empirical prior for the intensity works well when the actual outbreak time agrees with the prior. But when the outbreak occurs "earlier than expected", the alarms are seriously delayed. A non-informative prior, however, works well.
A NOTE ON ROTATABILITY
(University of Gothenburg, 1994-10-01) Ekman, Claes
The need of a measure of rotatability is discussed and exemplified through some examples. The examples also shows the difficulties with measuring rotatability. A graphical technique for exploring the variance function is discussed.
A Note on the Risk Behavior and Death of Homo Economicus
(2006) Johansson-Stenman, Olof; Department of Economics
Recent papers by Cox and Sadiraj (2006) and Rubinstein (2006) have pointed out that expected utility theory is more general than has sometimes been acknowledged, and can hence not be refuted as easily by means of experiments. While acknowledging this fact, this note nevertheless demonstrates that typical risk experimental results are impossible to reconcile with conventional dynamic consumption theory under risk, where people are time consistent and integrate all sources of income perfectly.
A Spatial Analysis of Foreign Aid and Civil Society
(2017-01) Vecci, Joseph; Zelinsky, Tomas; Dept. of Economics, University of Gothenburg
We use a Spatial Durbin Model to examine the relationship between civil society aid projects and measures of civil society including membership and participation in community groups and satisfaction with democracy in Nigeria and Uganda. We then study the effect of civil society aid programs on corruption, a proxy for elite capture. The spatial model allows us to estimate the effects of project spillovers that may indirectly impact non project areas. We find that civil society aid projects are associated with a decrease in the creation of community groups and attendance at community meetings in Nigeria. In Uganda, we find that civil society aid projects have a negative effect on the membership of community groups in neighboring areas. We also find that civil society projects have a positive effect on satisfaction with democracy, but they reduce satisfaction in neighbouring areas in both Nigeria and Uganda. Our corruption measures reveal that corruption has a positive direct correlation with civil society aid projects in Uganda. A number of robustness measures are used to account for selection.
A stepwise regression procedure applied to an international production study - a multiple inference solution
(University of Gothenburg, 1997-04-01) Johnsson, Tommy; Ivarsson, Inge
The aim of this paper is to apply a certain procedure for stepwise regression analysis to a problem included in a study of integrated international production. The question, which factors are important for the transnational company's trade behaviour in certain respects, have been analysed by means of traditional methods. Hence the more interesting findings on the subject are likely to be reported already and the results here are only to be regarded as supplementary ones. Comparisons between old and new outcomes, and to some extent the interpretations of them, is however one point here.
A Structural Model of Childcare, Welfare, and the Labor Supply of Single Mothers
(2002) Andrén, Thomas; Department of Economics
This paper considers the simultaneous relationship of the single mother's decision to choose paid childcare, welfare participation and labor supply, and estimates a structural model that allows for a free error covariance. We use a discrete approach to the choice of labor supply together with the discrete choices of utilized paid childcare and welfare participation, which allow formulating the model as a multiple-choice problem. The results show that there is an association between social assistance, paid childcare and labor supply, but that the relationship is non-symmetric. An increase in the social assistance norms has a relatively small effect on paid childcare utilization, but a relatively larger effect on the mean labor supply. In contrast, a corresponding reduction in the childcare cost has a relatively large effect on the social assistance utilization but a relatively small effect on the mean labor supply. Our estimates suggest that a decrease in childcare cost increases the labor supply of those working rather than encourages non-workers to start work, which implies that childcare cost is foremost a barrier to fulltime work rather then a barrier to work at all.
A theoretical framework explaining the mechanisms of nudging
(2019-03) Löfgren, Åsa; Nordblom, Katarina; Department of Economics, University of Gothenburg
In this paper we develop a theoretical model to clarify the underlying mechanisms that drive individual decision making and responses to behavioral interventions, such as nudges. The contribution of the paper is three-fold: First, the model provides a theoretical framework that comprehensively structures the individual decision-making process applicable to a wide range of choice situations. Second, we reduce the confusion regarding what should be called a nudge by oﬀering a clear classiﬁcation of behavioral interventions. We distinguish among what we label as pure nudges, preference nudges, and other behavioral interventions. Third, we identify the mechanisms behind the eﬀectiveness of behavioral interventions based on the structured decision-making process. Hence, the model can be used to predict under which circumstances, and in which choice situations, a nudge is likely to be eﬀective.
A TIPPETT-ADAPTIVE METHOD OF COMBINING INDEPENDENT STATISTICAL TESTS.
(University of Gothenburg, 1986-03-01) Westberg, Margareta
A new procedure is proposed in order to combine the information of P-values obtained from several independent tests in order to test an overall hypothesis. The test statistic of this new procedure is of the same type as Tippett's since in each step one of the P-values is compared with a constant. This new procedure is adaptive in the sense that the choice of P-value depends on the data. The procedure is very simple and in the performed examination this method is better than Tippett's in almost all situations. Thus this new "Tippett-adaptive" method is a good alternative to Tippett's procedure.
A Western Reversal since the Neolithic? The long-run impact of early agriculture
(2013-01) Olsson, Ola; Paik, Christopher; Dept of Economics, University of Gothenburg
While it is widely believed that regions which experienced a transition to Neolithic agriculture early also become institutionally and economically more advanced, many indicators suggest that within the Western agricultural core (including Europe, North Africa, the Middle East, and Southwest Asia), communities that adopted agriculture early in fact have weaker institutions and poorly functioning economies today. In the current paper, we attempt to integrate both of these trends in a coherent historical framework. Our main argument is that countries that made the transition early also tended to develop autocratic societies with social inequality and pervasive rent seeking, whereas later adopters were more likely to have egalitarian societies with stronger private property rights. These di¤erent institutional trajectories implied a gradual shift of dominance from the early civilizations towards regions in the periphery. We document this relative reversal within the Western core by showing a robust negative correlation between years since transition to agriculture and contemporary levels of income and institutional development, on both the national and the regional level. Our results further indicate that the reversal had become manifest already before the era of European colonization.

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