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The relationship between naturally fluoridated groundwater and dental fluorosis has received large attention from researchers around the world. Despite recognition that several factors influence this relationship, there is a lack of systematic studies analyzing the heterogeneity of these results. To fill such a gap, this study performs a systematic review and meta-analysis to understand which factors influence this relationship and how. Selected studies were sampled between 2007 and 2017 from Web of Science, PubMed, Google Scholar and Scopus using keywords and Boolean operators. Results of the systematic review show that dental fluorosis affects individuals of all ages, with the highest prevalence below 11, while the impact of other factors (gender, environmental conditions, diet and dental caries) was inconclusive. Meta-regression analysis, based on information collected through systematic review, indicates that both fluoride in drinking water and temperature influence dental fluorosis significantly and that these studies might be affected by publication bias. Findings show that fluoride negatively affects people's health in less developed countries. The conclusions discuss policy tools and technological innovations that could reduce fluoride levels below that of the World Health Organization (WHO) (<1.5 mg/L).

This paper deals with the finite-sample performance of a set of unit-root tests for cross-correlated panels. Most of the available macroeconomic time series cover short time periods. The lack of information, in terms of time observations, implies that univariate tests are not powerful enough to reject the null of a unit-root while panel tests, by exploiting the large number of cross-sectional units, have been shown to be a promising way of increasing the power of unit-root tests. We investigate the finite sample properties of recently proposed panel unit-root tests for cross-sectionally correlated panels. Specifically, the size and power of Choi's [Econometric Theory and Practice:

This paper analyses, within the new growth theory framework and using panel cointegration techniques, the effect of agricultural international technological spillovers on total factor productivity growth for a sample of 47 countries during the period 1970-1992. The analysis shows that total factor productivity is strongly influenced by domestic as well as foreign public R&D spending in agricultural sector and geographical factors matters. Countries located in temperate zones benefit more than countries located in tropical zones from technological spillovers. Finally, the analysis shows that the rate of return to agricultural R&D spending is higher in tropical countries and this could justify new support and an even greater investment of funds for agricultural R&D for these countries.