Productivity of the Science and Technology (S&T) sector of Latin American countries would require more public and private investment to increase. Despite significant progress in the first 15 years of this century, South American investment in Science as percentage of GDP has been 10- fold lower than that of Europe. Though the need to increase S&T investment is clear, less obvious is whether money should go to infrastructure or human capital. Using global databases we assessed scientific productivity, number of researchers and resources devoted to S&T. We evaluated production for Europe, the Americas and China. We then focused on three Mercosur countries: Argentina, Brazil and Uruguay. Scientific production was related to S&T expenditure and to the number of researchers. We found that countries investing ~2% of their GDP may have a 5-fold variation in their productivity. Our results suggest that human capital explains a higher proportion of the S&T productivity than the total amount of resources devoted to science. Thus, people would matter more than infrastructure in determining the scientific output. The positive trends in the resources devoted to Science in Argentina, Brazil and Uruguay do not allow, though, to reach in a decade the levels of productivity of European countries.