In some ways, trying to describe and understand all facets of development around the world is a ridiculous task. The previous sections of this chapter barely scratch the surface, and yet the major questions pertaining to development are actually quite simple. Is it better for a country to be intricately connected to the global economy and to willingly import and export lots of things? Or is it better to close oneself off, protecting your own from the potential dangers of the outside world? History seems to be on the side of openness, but that also carries serious risk. Governments can spend huge amounts of money trying to make people’s lives better only to find themselves in massive debt, followed by massive political upheaval (as recently happened in Brazil). There is no single magical formula, yet the general principles laid out in this chapter do offer some valuable insight from what has occurred in the past 70 years. On average, human beings in the 21st century are healthier, living longer, earning more money, having fewer children, consuming more, and knowing more about their world than at any other time in the history of our species. Given these realities, there is reason for cautious optimism as we look forward to the next hundred years. In spite of all of that, it’s imperative that we realize the fragility of our planet and the environmental cost that comes with the overconsumption of resources. As large countries like China become wealthier, hundreds of millions of new consumers create more plastic waste, more toxic runoff, more carbon emissions, more copper mines, and more demand for energy than ever before. The rush to development has often hastened ecological catastrophe, making it essential that future development efforts consider long-term sustainability as an anchor for decision-making in the 21st century and beyond.