The burden that humanity places on the planet depends, in part, on the number of people. Since 1950, world population has grown from 2.5 billion to nearly 7.3 billion. Based on current trends in fertility rates and lifespan, the United Nations projects a global population of 10.9 billion by the end of the century. However, the UN does not explicitly model the effect of average levels of education, particularly among women in developing nations. According to a recent study by the International Institute for Applied Systems Analytics (IIASA), variations in the average level of education can have a dramatic effect, with projected population for 2100 as low as 7.1 billion and as high as 12.8 billion. On the path to a world that guarantees well-being for all on our resource-constrained planet, universal access to high quality education is thus an essential step.