G-1 Appeal Activity in the Public Assistance Programs, December 2007

The Food Assistance Monthly Participation Report is a monthly summary of Food Assistance program participation, Statewide and for each Iowa county. Breakouts are reported for participants also in the FIP program, those only receiving Food Assistance, and those that are receiving economic assistance under other programs (primarily Medicaid). This report may also be known as the F-1 Report.

Otimização Não Linear de Mínimos Quadrados

O problema de otimização de mínimos quadrados e apresentado como uma classe importante de problemas de minimização sem restrições. A importância dessa classe de problemas deriva das bem conhecidas aplicações a estimação de parâmetros no contexto das analises de regressão e de resolução de sistemas de equações não lineares. Apresenta-se uma revisão dos métodos de otimização de mínimos quadrados lineares e de algumas técnicas conhecidas de linearização. Faz-se um estudo dos principais métodos de gradiente usados para problemas não lineares gerais: Métodos de Newton e suas modificações incluindo os métodos Quasi-Newton mais usados (DFP e BFGS). Introduzem-se depois métodos específicos de gradiente para problemas de mínimos quadrados: Gauss-Newton e Levenberg-Larquardt. Apresenta-se uma variedade de exemplos selecionados na literatura para testar os diferentes métodos usando rotinas MATLAB. Faz-se uma an alise comparativa dos algoritmos baseados nesses ensaios computacionais que exibem as vantagens e desvantagens dos diferentes métodos.

A general decomposition formula for derivative prices in stochastic volatility models

We see that the price of an european call option in a stochastic volatilityframework can be decomposed in the sum of four terms, which identifythe main features of the market that affect to option prices: the expectedfuture volatility, the correlation between the volatility and the noisedriving the stock prices, the market price of volatility risk and thedifference of the expected future volatility at different times. We alsostudy some applications of this decomposition.

On certain greedoid polyhedra, partially indexable scheduling problems and extended restless bandit allocation indices

We present a polyhedral framework for establishing general structural properties on optimal solutions of stochastic scheduling problems, where multiple job classes vie for service resources: the existence of an optimal priority policy in a given family, characterized by a greedoid(whose feasible class subsets may receive higher priority), where optimal priorities are determined by class-ranking indices, under restricted linear performance objectives (partial indexability). This framework extends that of Bertsimas and Niño-Mora (1996), which explained the optimality of priority-index policies under all linear objectives (general indexability). We show that, if performance measures satisfy partial conservation laws (with respect to the greedoid), which extend previous generalized conservation laws, then theproblem admits a strong LP relaxation over a so-called extended greedoid polytope, which has strong structural and algorithmic properties. We present an adaptive-greedy algorithm (which extends Klimov's) taking as input the linear objective coefficients, which (1) determines whether the optimal LP solution is achievable by a policy in the given family; and (2) if so, computes a set of class-ranking indices that characterize optimal priority policies in the family. In the special case of project scheduling, we show that, under additional conditions, the optimal indices can be computed separately for each project (index decomposition). We further apply the framework to the important restless bandit model (two-action Markov decision chains), obtaining new index policies, that extend Whittle's (1988), and simple sufficient conditions for their validity. These results highlight the power of polyhedral methods (the so-called achievable region approach) in dynamic and stochastic optimization.

Audit report on the Iowa Water Pollution Control Works Financing Program and the Iowa Drinking Water Facilities Financing Program, joint programs of the Iowa Finance Authority and the Iowa Department of Natural Resources for the year ended June 30, 2007

Audit report on the Iowa Water Pollution Control Works Financing Program and the Iowa Drinking Water Facilities Financing Program, joint programs of the Iowa Finance Authority and the Iowa Department of Natural Resources for the year ended June 30, 2007

Restless bandits, partial conservation laws and indexability

We show that if performance measures in a stochastic scheduling problem satisfy a set of so-called partial conservation laws (PCL), which extend previously studied generalized conservation laws (GCL), then the problem is solved optimally by a priority-index policy for an appropriate range of linear performance objectives, where the optimal indices are computed by a one-pass adaptive-greedy algorithm, based on Klimov's. We further apply this framework to investigate the indexability property of restless bandits introduced by Whittle, obtaining the following results: (1) we identify a class of restless bandits (PCL-indexable) which are indexable; membership in this class is tested through a single run of the adaptive-greedy algorithm, which also computes the Whittle indices when the test is positive; this provides a tractable sufficient condition for indexability; (2) we further indentify the class of GCL-indexable bandits, which includes classical bandits, having the property that they are indexable under any linear reward objective. The analysis is based on the so-called achievable region method, as the results follow fromnew linear programming formulations for the problems investigated.

Solving higher-dimensional continuous time stochastic control problems by value function regression

The paper develops a method to solve higher-dimensional stochasticcontrol problems in continuous time. A finite difference typeapproximation scheme is used on a coarse grid of low discrepancypoints, while the value function at intermediate points is obtainedby regression. The stability properties of the method are discussed,and applications are given to test problems of up to 10 dimensions.Accurate solutions to these problems can be obtained on a personalcomputer.

G-1 Appeal Activity in the Public Assistance Programs

This report contains information on the Appeal Activity in the Public Assistance Programs. Programs included are FIP (Iowa’s TANF program), Title IV-D (Child Support), Food Stamps (USDA Food Assistance Program), Title XIX (Medicaid), Title XX (Social Services Block Grant), Juvenile Parole, State Supplemental Assistance, Other, Food Stamp Fraud, FIP Fraud, RCA (Refugee Cash Assistance) Fraud, and a total for all the programs. This report is issued monthly.

G-1 Appeal Activity in the Public Assistance Programs, February 2008

This report contains information on the Appeal Activity in the Public Assistance Programs. Programs included are FIP (Iowa’s TANF program), Title IV-D (Child Support), Food Stamps (USDA Food Assistance Program), Title XIX (Medicaid), Title XX (Social Services Block Grant), Juvenile Parole, State Supplemental Assistance, Other, Food Stamp Fraud, FIP Fraud, RCA (Refugee Cash Assistance) Fraud, and a total for all the programs. This report is issued monthly.

G-1 Appeal Activity in the Public Assistance Programs, March 2008

This report contains information on the Appeal Activity in the Public Assistance Programs. Programs included are FIP (Iowa’s TANF program), Title IV-D (Child Support), Food Stamps (USDA Food Assistance Program), Title XIX (Medicaid), Title XX (Social Services Block Grant), Juvenile Parole, State Supplemental Assistance, Other, Food Stamp Fraud, FIP Fraud, RCA (Refugee Cash Assistance) Fraud, and a total for all the programs. This report is issued monthly.

G-1 Appeal Activity in the Public Assistance Programs, April 2008

This report contains information on the Appeal Activity in the Public Assistance Programs. Programs included are FIP (Iowa’s TANF program), Title IV-D (Child Support), Food Stamps (USDA Food Assistance Program), Title XIX (Medicaid), Title XX (Social Services Block Grant), Juvenile Parole, State Supplemental Assistance, Other, Food Stamp Fraud, FIP Fraud, RCA (Refugee Cash Assistance) Fraud, and a total for all the programs. This report is issued monthly.

G-1 Appeal Activity in the Public Assistance Programs, May 2008

This report contains information on the Appeal Activity in the Public Assistance Programs. Programs included are FIP (Iowa’s TANF program), Title IV-D (Child Support), Food Stamps (USDA Food Assistance Program), Title XIX (Medicaid), Title XX (Social Services Block Grant), Juvenile Parole, State Supplemental Assistance, Other, Food Stamp Fraud, FIP Fraud, RCA (Refugee Cash Assistance) Fraud, and a total for all the programs. This report is issued monthly.

Measuring and explaining farm inefficiency in a panel data set of mixed farms

This paper aims to estimate a translog stochastic frontier production function in the analysis of a panel of 150 mixed Catalan farms in the period 1989-1993, in order to attempt to measure and explain variation in technical inefficiency scores with a one-stage approach. The model uses gross value added as the output aggregate measure. Total employment, fixed capital, current assets, specific costs and overhead costs are introduced into the model as inputs. Stochasticfrontier estimates are compared with those obtained using a linear programming method using a two-stage approach. The specification of the translog stochastic frontier model appears as an appropriate representation of the data, technical change was rejected and the technical inefficiency effects were statistically significant. The mean technical efficiency in the period analyzed was estimated to be 64.0%. Farm inefficiency levels were found significantly at 5%level and positively correlated with the number of economic size units.

Exact tests for correlation and for the slope in simple linear regressions without making assumptions

We present an exact test for whether two random variables that have known bounds on their support are negatively correlated. The alternative hypothesis is that they are not negatively correlated. No assumptions are made on the underlying distributions. We show by example that the Spearman rank correlation test as the competing exact test of correlation in nonparametric settings rests on an additional assumption on the data generating process without which it is not valid as a test for correlation.We then show how to test for the significance of the slope in a linear regression analysis that invovles a single independent variable and where outcomes of the dependent variable belong to a known bounded set.

G-1 Appeal Activity in the Public Assistance Programs, June 2008

This report contains information on the Appeal Activity in the Public Assistance Programs. Programs included are FIP (Iowa’s TANF program), Title IV-D (Child Support), Food Stamps (USDA Food Assistance Program), Title XIX (Medicaid), Title XX (Social Services Block Grant), Juvenile Parole, State Supplemental Assistance, Other, Food Stamp Fraud, FIP Fraud, RCA (Refugee Cash Assistance) Fraud, and a total for all the programs. This report is issued monthly.