There is a challenge for this chapter. Coming this far in the book you have learned a little about population growth, and you have access to computer coding, so you are ready for something big.
Imagine for fun that you have accepted a new job in Washington as a policy fellow with the United States Geological Survey, or USGS—one of the major research branches of the federal government. This is not farfetched; many recent doctoral graduates land such jobs at reasonably high levels. But suppose that your boss says she wants you to calculate what the world’s population will be in 2100. Other agencies have done this, but she wants a separate USGS estimate, presented in an understandable way. She can give you data from the 18th through the 21st centuries. She discloses that she is meeting with the Secretary General of the United Nations tomorrow and hopes you can figure it out today. You tell her “Sure, no problem.”
Are you crazy? No! The rest of this chapter will walk you through how to it. We’ll start by piecing together the parts, as in Figure 4.4.1-the orthologistic part, if there is one, and any exponential and logistic parts as well.