Using a large unbalanced panel data set of Portuguese manufacturing firms surviving over the period from 1990 to 2001, the purpose of this paper is to examine whether liquidity constraints faced by business firms affect firm growth. We use a GMM-system to estimate a dynamic panel data model of firm growth tha t incorporates cash flow as a measure of liquidity constraints and persistence of growth. The model is estimated for all size classes, including micro firms. Our findings suggest that smaller and younger firms have higher growth-cash flow sensitivities tha n larger and more mature firms. This is consistent with the suggestion that financial constraints on firm growth may be relatively more severe for small and young firms. Finally, firms that were small and young and strongly liquidity-constrained at the beginning of the sample period exhibited more persistent growth than those that were large and old and weakly liquidity-constrained. These results have significant policy implications.

The purpose of this paper is to use Dynamic Panel Data (DPD) models to see if Gibrat's law holds and to analyse the empirical determinants of firm growth. This paper makes significant contributions to the empirical literature on the dynamics of firm growth, since it updates the work carried out by previous researchers in this field using micro panel data and GMM estimators. To conduct this study we use an unbalanced panel of Portuguese manufacturing firms over the period from 1990 to 1999. The main implication of our findings is that firm growth is not quite random since there are some determinants which exert influence on firm growth. JEL classification: L11, C23.

Firm growth, Panel data, GMM estimators, Services, L11, C23, L80,

A residential water demand equation is estimated using a panel data sample of 5Portuguese local communities and 72 months, corresponding to a total number of 360 observations. Because of the presence of multi-part tariffs, we use as explanatory variables the two common price-related variables: marginal price and difference. To prevent the simultaneity bias from using observed quantities to determine the values of marginal price and difference directly from the rate schedule, we use an instrumental variable approach to create a constant marginal price and difference parameters for each rate structure.The price elasticity value obtained fall within the range of those found in other case studies. Thus, although presenting weak elasticity, price seems to play a role in water demand management. However, we do not confirm the expected influence of difference on residential water demand. This can be a consequence of the complexity of the Portuguese water tariffs and the confusing signs that come from the simultaneous use of fixed quotas and increasing block tariffs. So, it is imperative to clarify water tariffs objectives by reviewing the Portuguese water tariffs design processes.

There is a consensus that the emphasis on the management of water resources should be put on demand side policies. However, some questions remain to be solved on the supply side, which are frequently absent from empirical studies based on the estimation of cost functions. This paper aims to fill to some extent this gap in the literature by focusing the consequences of water losses reduction and the management of water resources based on their availability at an integrated river basin level.Major findings indicate that it would be better in terms of costs to maintain some level of water losses than to repair the leaks and suggest advantages from more concentration in the Portuguese water industry. In addition, the costs do not seem to be systematically influenced by the hydrographical regions to which water utilities belong, what might be due to the absence of appropriate cost accounting methods.JEL Classification: L11, L95, Q25