The stopping of swift protons in matter and its implication for astrophysical fusion reactions

The velocity dependence of the stopping power of swift protons and deuterons in low energy collisions is investigated. At low projectile energies the stopping is mainly due to nuclear stopping and charge exchange of the electron. The second mechanism dominates after Ep >=200 eV. A dynamical treatment of the charge exchange mechanism based on two-center electronic wavefunctions yields very transparent results for the exchange probability. We predict that the stopping cross sections vary approximately as v to the 1.35 power for projectile protons on hydrogen targets in the 1 keV energy region.Comment: 4 figure

“Value Added Taxes, Chain Effects and Informality”, Second Version

This paper investigates determinants of informal economic activity. We present an equilibrium model of informality and test its implications using a survey of 48,000+ small firms in Brazil. We define informality as tax avoidance; firms in the informal sector avoid tax payments but suffer other limitations. A novel theoretical contribution in this model is the role of value added taxes in transmitting informality. It predicts that the informality of a firm is correlated to the informality of firms from which it buys or sells. The model also implies that higher tolerance for informal firms in one production stage increases tax avoidance in downstream and upstream stages. Empirical analysis shows that, in fact, various measures of formality of suppliers and purchasers (and its enforcement) are correlated with the formality of a firm. Even more interestingly, when we look at sectors where Brazilian firms are not subject to the credit system of value added tax, but instead the value added tax is applied at some stage of production at a rate that is estimated by the tax authorities, this chain effect vanishes.Informal Sector, VAT, Tax Avoidance

The Informal Sector: An Equilibrium Model and Some Empirical Evidence from Brazil, Second Version

We test implications of a simple equilibrium model of informality using a survey of 48,000+ small firms in Brazil. In the model, agent's ability to manage production differ and informal firms face a higher cost of capital and limitation on size, although these informal firms avoid tax payments. As a result, informal firms are managed by less able entrepreneurs, are smaller, and employ a lower capital-labor ratio. The model predicts that the interaction of an index of observable inputs to entrepreneurial ability and formality is positively correlated with firm size, which we verify in the data. Using the model, we estimate that informal firms in our dataset faced at least 1.3 times the cost of capital of formal firms.Informal Sector, Tax Avoidance, Brazil

The Informal Sector, Third Version

This paper investigates the determinants of informal economic activity. We present two equilibrium models of informality and test their implications using a survey of 48,000+ small firms in Brazil. We define informality as tax avoidance; firms in the informal sector avoid tax payments but suffer other limitations. In the first model there is a single industry and informal firms face a higher cost of capital and a limitation on size. As a result informal firms are smaller and have a lower capital-labor ratio. When education is an imperfect proxy for ability, we show that the interaction of the manager's education and formality has a positive correlation with firm size. These implications are supported by our empirical analysis. A novel theoretical contribution in this paper is a model that highlights the role of value added taxes in transmitting informality. It predicts that the informality of a firm is correlated to the informality of firms from which it buys or sells. The model also implies that higher tolerance for informal firms in one production stage increases tax avoidance in downstream and upstream sectors. Empirical analysis shows that, in fact, various measures of formality of suppliers and purchasers (and its enforcement) are correlated with the formality of a firm. Even more interestingly, when we look at sectors where Brazilian firms are not subject to the credit system of value added tax, but instead the value added tax is applied at some stage of production at a rate that is estimated by the State, this chain effect vanishes.Informal Sector, VAT, Tax Avoidance

Value Added Taxes, Chain Effects and Informality

This paper investigates determinants of informal economic activity. We present an equilibrium model of informality and test its implications using a survey of 48,000+ small firms in Brazil. We define informality as tax avoidance; firms in the informal sector avoid tax payments but suffer other limitations. A novel theoretical contribution in this model is the role of value added taxes in transmitting informality. It predicts that the informality of a firm is correlated to the informality of firms from which it buys or sells. The model also implies that higher tolerance for informal firms in one production stage increases tax avoidance in downstream and upstream stages. Empirical analysis shows that, in fact, various measures of formality of suppliers and purchasers (and its enforcement) are correlated with the formality of a firm. Even more interestingly, when we look at sectors where Brazilian firms are not subject to the credit system of value added tax, but instead the value added tax is applied at some stage of production at a rate that is estimated by the tax authorities, this chain effect vanishes.Informal Sector,VAT,Tax Avoidance

The Informal Sector

This paper investigates the determinants of informal economic activity. We present two equilibrium models of informality and test their implications using a survey of 48,000+ small firms in Brazil. We define informality as tax avoidance; firms in the informal sector avoid tax payments but suffer other limitations. In the first model there is a single industry and informal firms face a higher cost of capital and a limitation on size. As a result informal firms are smaller and have a lower capital labor ratio. When education is an imperfect proxy for ability, we show that the interaction of the manager's education and formality has a positive correlation with firm size. These implications are supported by our empirical analysis. The second model highlights the role of value added taxes in transmitting informality. It predicts that the informality of a firm is correlated to the informality of firms from which it buys or sells. The model implies that higher tolerance for informal firms in one production stage increases tax avoidance in downstream and upstream sectors. Empirical analysis shows that, in fact, various measures of formality of suppliers and purchasers (and its enforcement) are correlated with the formality of a firm. Even more interestingly, when we look at sectors where Brazilian firms are not subject to the credit system of value added tax, this chain effect vanishes.

The Informal Sector: An Equilibrium Model and Some Empirical Evidence from Brazil

We test implications of a simple equilibrium model of informality using a survey of 48,000+ small firms in Brazil. In the model, agent's ability to manage production differ and informal firms face a higher cost of capital and limitation on size, although these informal firms avoid tax payments. As a result, informal firms are managed by less able entrepreneurs, are smaller and employ a lower capital-labor ratio. When education is an imperfect proxy for ability, the model predicts that the interaction of the manager's education and formality is positively correlated with firm size. Using the model, we estimate that informal firms in our dataset faced at least 1.3 times the cost of capital of formal firms.Informal Sector, Tax Avoidance, Brazil