Tax Structure, Growth and Welfare in the UK

This paper studies the quantitative implications of changes in the composition of taxes for long-run growth and expected lifetime utility in the UK economy over 1970-2005. Our setup is a dynamic stochastic general equilibrium model incorporating a detailed scal policy struc- ture, and where the engine of endogenous growth is human capital accumulation. The government s spending instruments include pub- lic consumption, investment and education spending. On the revenue side, labour, capital and consumption taxes are employed. Our results suggest that if the goal of tax policy is to promote long-run growth by altering relative tax rates, then it should reduce labour taxes while simultaneously increasing capital or consumption taxes to make up for the loss in labour tax revenue. In contrast, a welfare promoting policy would be to cut capital taxes, while concurrently increasing labour or consumption taxes to make up for the loss in capital tax revenue.

Do political incentives matter for tax policies? Ideology, opportunism and the tax structure

This paper investigates the importance of political ideology and opportunism in the choice of the tax structure. In particular, we examine the effects of cabinet ideology and elections on the distribution of the tax burden across factors of production and consumption for 21 OECD countries over the period 1970-2000 by employing four alternative cabinet ideology measures and by using the methodology of effective tax rates. There is evidence of both opportunistic and partisan effects on tax policies. More precisely, we find that left-wing governments rely more on capital relative to labor income taxation and that they tend to increase consumption taxes. Moreover, we find that income tax rates (but not consumption taxes) tend to be reduced in preelectoral periods and that capital effective tax rates (defined broadly to include taxes on selfemployed income) are reduced by more than effective labor tax rates.

Screening of highly modular sugar-based ligand libraries in the enantioselective C-C coupling reactions

Projecte de recerca elaborat a partir d’una estada a la University of Nottingham, Gran Bretanya, entre març i abril del 2007. Aquest treball s’ha centrat en l’aplicació de compostos derivats de la D-(+)-glucosa, de la D-(+)-fructosa i la D-galactosa com a lligands de catalitzadors homogenis quirals en dos reaccions asimètriques: addició 1,2 a aldehids catalitzada per níquel i addició 1,4 conjugada catalitzada per coure.(veure figura adjunta al final del document). En primer lloc, s’ha estudiat l’aplicació dels compostos L1-L6 a les reaccions d’addició 1,2 a aldehids catalitzades per níquel. S’ha observat que la selectivitat del procés depèn principalment del grup funcional unit a l’esquelet del lligand, de les propietats estèriques del substituent en la funció oxazolina i de l’estructura del substrat. S’ha obtingut fins a un 59% d’excés enantiomèric utilitzant el precursor de catalitzador que conté el lligand L3a. En segon lloc, aquest treball descriu l’aplicació de les tres famílies de compostos (L1-L11) com a lligands en la reacció d’addició 1,4 catalitzada per coure de compostos organometàl•lics a diferents enones amb diferents propietats estèriques. L’ús de les llibreries de compostos fosfit-oxazolina (L1-L5) i fosfit-fosforamidit (L6) han proporcionat bones enantioselectivitats (fins a 80%) en l’addició de reactius de trialquilalumini a diferents enones. En canvi, la llibreria de compostos monofosfit (L7-L11) ha mostrat bones activitats però enantioselectivitats fins a 57%.

Industrial Structure, Trade and Regional Economics : Market Segmentation

We consider a general equilibrium model a la Bhaskar (Review of Economic Studies 2002): there are complementarities across sectors, each of which comprise (many) heterogenous monopolistically competitive firms. Bhaskar's model is extended in two directions: production requires capital, and labour markets are segmented. Labour market segmentation models the difficulties of labour migrating across international barriers (in a trade context) or from a poor region to a richer one (in a regional context), whilst the assumption of a single capital market means that capital flows freely between countries or regions. The model is solved analytically and a closed form solution is provided. Adding labour market segmentation to Bhaskar's two-tier industrial structure allows us to study, inter alia, the impact of competition regulations on wages and - financial flows both in the regional and international context, and the output, welfare and financial implications of relaxing immigration laws. The analytical approach adopted allows us, not only to sign the effect of policies, but also to quantify their effects. Introducing capital as a factor of production improves the realism of the model and refi nes its empirically testable implications.

The Changing Inter-Industry Wage Structure of the Organised Manufacturing Sector in India, 1973-74 to 2003-04

This study examines the inter-industry wage structure of the organised manufacturing sector in India for the period 1973-74 to 2003-04 by estimating the growth of average real wages for production workers by industry. In order to estimate the growth rates, the study adopts a methodological framework that differs from other studies in that the time series properties of the concerned variables are closely considered in order to obtain meaningful estimates of growth that are unbiased and (asymptotically) efficient. Using wage data on 51 manufacturing industries at three digit level of the National Industrial Classification 1998 (India), our estimation procedure obtains estimates of growth of real wages per worker that are deterministic in nature by accounting for any potential structural break(s). Our findings show that the inter-industry wage structure in India has changed a lot in the period 1973-74 to 2003-04 and that it provides some evidence that the inter-industry wage differences have become more pronounced in the post-reforms period. Thus this paper provides new evidence from India on the need to consider the hypothesis that industry affiliation is potentially an important determinant of wages when studying any relationship between reforms and wages.

A model category structure on the category of simplicial multicategories

We establish a Quillen model structure on simplicial(symmetric) multicategories. It extends the model structure on simplicial categories due to J. Bergner [2]. We observe that our technique of proof enables us to prove a similar result for (symmetric) multicategories enriched over other monoidal model categories than simplicial sets. Examples include small categories, simplicial abelian groups and compactly generated Hausdorff spaces.

A Thomason model structure on the category of small n-fold categories

We construct a cofibrantly generated Thomason model structure on the category of small n-fold categories and prove that it is Quillen equivalent to the standard model structure on the category of simplicial sets. An n-fold functor is a weak equivalence if and only if the diagonal of its n-fold nerve is a weak equivalence of simplicial sets. We introduce an n-fold Grothendieck construction for multisimplicial sets, and prove that it is a homotopy inverse to the n-fold nerve. As a consequence, the unit and counit of the adjunction between simplicial sets and n-fold categories are natural weak equivalences.

Bacterial community structure of a pesticide-contaminated site and assessment of changes induced in community structure during bioremediation.

The introduction of culture-independent molecular screening techniques, especially based on 16S rRNA gene sequences, has allowed microbiologists to examine a facet of microbial diversity not necessarily reflected by the results of culturing studies. The bacterial community structure was studied for a pesticide-contaminated site that was subsequently remediated using an efficient degradative strain Arthrobacter protophormiae RKJ100. The efficiency of the bioremediation process was assessed by monitoring the depletion of the pollutant, and the effect of addition of an exogenous strain on the existing soil community structure was determined using molecular techniques. The 16S rRNA gene pool amplified from the soil metagenome was cloned and restriction fragment length polymorphism studies revealed 46 different phylotypes on the basis of similar banding patterns. Sequencing of representative clones of each phylotype showed that the community structure of the pesticide-contaminated soil was mainly constituted by Proteobacteria and Actinomycetes. Terminal restriction fragment length polymorphism analysis showed only nonsignificant changes in community structure during the process of bioremediation. Immobilized cells of strain RKJ100 enhanced pollutant degradation but seemed to have no detectable effects on the existing bacterial community structure.

The twist, writhe and overall shape of supercoiled DNA change during counterion-induced transition from a loosely to a tightly interwound superhelix. Possible implications for DNA structure in vivo.

A cryo-electron microscopy study of supercoiled DNA molecules freely suspended in cryo-vitrified buffer was combined with Monte Carlo simulations and gel electrophoretic analysis to investigate the role of intersegmental electrostatic repulsion in determining the shape of supercoiled DNA molecules. It is demonstrated here that a decrease of DNA-DNA repulsion by increasing concentrations of counterions causes a higher fraction of the linking number deficit to be partitioned into writhe. When counterions reach concentrations likely to be present under in vivo conditions, naturally supercoiled plasmids adopt a tightly interwound conformation. In these tightly supercoiled DNA molecules the opposing segments of interwound superhelix seem to directly contact each other. This form of supercoiling, where two DNA helices interact laterally, may represent an important functional state of DNA. In the particular case of supercoiled minicircles (178 bp) the delta Lk = -2 topoisomers undergo a sharp structural transition from almost planar circles in low salt buffers to strongly writhed "figure-eight" conformations in buffers containing neutralizing concentrations of counterions. Possible implications of this observed structural transition in DNA are discussed.

Modeling Dependence Structure and Forecasting Portfolio Value-at-Risk with Dynamic Copulas

We study the asymmetric and dynamic dependence between financial assets and demonstrate, from the perspective of risk management, the economic significance of dynamic copula models. First, we construct stock and currency portfolios sorted on different characteristics (ex ante beta, coskewness, cokurtosis and order flows), and find substantial evidence of dynamic evolution between the high beta (respectively, coskewness, cokurtosis and order flow) portfolios and the low beta (coskewness, cokurtosis and order flow) portfolios. Second, using three different dependence measures, we show the presence of asymmetric dependence between these characteristic-sorted portfolios. Third, we use a dynamic copula framework based on Creal et al. (2013) and Patton (2012) to forecast the portfolio Value-at-Risk of long-short (high minus low) equity and FX portfolios. We use several widely used univariate and multivariate VaR models for the purpose of comparison. Backtesting our methodology, we find that the asymmetric dynamic copula models provide more accurate forecasts, in general, and, in particular, perform much better during the recent financial crises, indicating the economic significance of incorporating dynamic and asymmetric dependence in risk management.

Structure of a multisubunit complex that promotes DNA branch migration.

The RuvA and RuvB proteins of Escherichia coli, which are induced in response to DNA damage, are important in the formation of heteroduplex DNA during genetic recombination and related recombinational repair processes. In vitro studies show that RuvA binds Holiday junctions and acts as a specificity factor that targets the RuvB ATPase, a hexameric ring protein, to the junction. Together, RuvA and RuvB promote branch migration, an ATP-dependent reaction that increases the length of the heteroduplex DNA. Electron microscopic visualization of RuvAB now provides a new insight into the mechanism of this process. We observe the formation of a tripartite protein complex in which RuvA binds the crossover and is sandwiched between two hexameric rings of RuvB. The Holliday junction within this complex adopts a square-planar structure. We propose a molecular model for branch migration, a unique feature of which is the role played by the two oppositely oriented RuvB ring motors.

Term Structure Dynamics, Macro-Finance Factors and Model Uncertainty

This paper extends the Nelson-Siegel linear factor model by developing a flexible macro-finance framework for modeling and forecasting the term structure of US interest rates. Our approach is robust to parameter uncertainty and structural change, as we consider instabilities in parameters and volatilities, and our model averaging method allows for investors' model uncertainty over time. Our time-varying parameter Nelson-Siegel Dynamic Model Averaging (NS-DMA) predicts yields better than standard benchmarks and successfully captures plausible time-varying term premia in real time. The proposed model has significant in-sample and out-of-sample predictability for excess bond returns, and the predictability is of economic value.

Modeling Dependence Structure and Forecasting Market Risk with Dynamic Asymmetric Copula

We investigate the dynamic and asymmetric dependence structure between equity portfolios from the US and UK. We demonstrate the statistical significance of dynamic asymmetric copula models in modelling and forecasting market risk. First, we construct “high-minus-low" equity portfolios sorted on beta, coskewness, and cokurtosis. We find substantial evidence of dynamic and asymmetric dependence between characteristic-sorted portfolios. Second, we consider a dynamic asymmetric copula model by combining the generalized hyperbolic skewed t copula with the generalized autoregressive score (GAS) model to capture both the multivariate non-normality and the dynamic and asymmetric dependence between equity portfolios. We demonstrate its usefulness by evaluating the forecasting performance of Value-at-Risk and Expected Shortfall for the high-minus-low portfolios. From back-testing, e find consistent and robust evidence that our dynamic asymmetric copula model provides the most accurate forecasts, indicating the importance of incorporating the dynamic and asymmetric dependence structure in risk management.