The course of the post-Mao era, a distinct tendency arose for forecasts by China watchers to polarise between pessimism and optimism. A degree of optimism about China's post-Mao development gives a profound scepticism. Scepticism reached new heights with two best-sellers published by Peter Navarro titled The Coming China Wars and Death by China. Increasing confidence about China's prospects among some foreign analysts was soon challenged once more at the turn of the century by a vigorous reassertion of the case for pessimism. During the second half of the 2000s, several experts produced very optimistic forecasts for China's economic future. Robert Fogel calculated that in 2040 its economy would reach US $123 trillion, measured by purchasing power parity (PPP). This would be almost three times the gross domestic product (GDP) of the US and 40 percent of total global GDP. Deutsche Bank concluded that GDP growth of 7 percent or even two decades was achievable if reforms continued.