The multiple attempts at empirical evidence, yet recent, fail to truly dispel the theoretical vagueness of the effects of public debt on economic growth. The aim of this work is to demonstrate that public overindebtedness negatively impacts economic activity in developing countries. From estimation by the generalized moments' method in the system of the relationship between economic growth and outstanding public debt on data of the Gabonese economy, we get that an increase in the public debt in this country, causes a deceleration of economic activity, thus reflecting a scissor effect between public debt trend and that of economic growth.

Taking into account the effects of financial liberalization on activity, associated with the spread of financial crises in an environment of uncertainty and dependence of the economies on external financing, updates the question of the impact of external capital on growth economic. The purpose of this paper is to examine the impact of external capital on economic growth in developing country members of a monetary union. Following a dynamic least squares estimation on the data of the countries of the Economic and Monetary Community of Central Africa (EMCCA), we obtain that an increase in direct investment abroad positively influences the economic growth in these countries.

In the absence of adjustment by exchange rates, it is suggested that the effects of a devaluation of the exchange rate through taxation be produced.The purpose of our study is thus to examine the plausibility of such an option in developing countries participating in a monetary union. From a normative perspective, we proceed to an empirical highlighting of the mechanism of classic fiscal devaluation, thanks to the estimation of a model with threshold effects on the data of the Gabonese economy.As a result, the option of fiscal devaluation is conceivable for Gabon. But, its effects would be small.

Tax pressure is pointed out as one of the main causes for the development of informality. To the extent that the informal economy is perceived, inter alia, as a response to excessive and inappropriate public regulation. The purpose of our study is mainly to verify such a relationship in the context of the Gabonese economy thanks to the estimation of a model with changes of regimes of the individual time series at the Hansen [1]. Overall, the impact of tax repression on the informal economy differs depending on the level of the tax rate. In other words, there are two growth regimes in the informal sector conditional on a tax threshold of 7.10%.