According to estimates, $1.8 trillion was invested in energy around the world in 2017. That's down 2% from 2016 and the third straight year of global declines.However, that trend isn't expected to continue. The global middle class is growing, and that's driving demand for energy steadily higher. It's also going to take a combination of growth in renewables and fossil fuel development to meet that need -- and that means a lot of opportunity for investors in the years ahead. Image source: Getty Images.Continue reading