The world's population reached 8 billion on Tuesday, growing by 1 billion in the last dozen years and reflecting the rapid population spike of the past few decades, with India projected to become the world's most populous country by next year, surpassing China.While it took hundreds of thousands of years for the world's population to reach 1 billion, the world grew from 7 billion to 8 billion just since 2010, a reflection of advancements in health.As the world is expected to grow even more to over 10 billion during the next 60 years as the U.N.'s population division of the Department of Economic and Social Affairs (DESA) reported, population growth is slowing relative to the past, and the U.N. warns that the challenges of feeding, housing and keeping that level of people from polluting the climate will be significant.The '8 billion' person number is also a wake-up call for the U.S. since the report says that global migration "will be the sole driver of population growth in high-income countries."That's because the combination of antiquated census gathering in many countries as well as proliferation of conflicts and the COVID19 pandemic, made a door-to-door count difficult, and the numbers are based in some countries on projections."