A "rate of change" is how fast one quantity shifts compared to another over time or input. In math, it's the slope or derivative, showing increase, decrease, or steady behavior.
Hominid and human evolution took place over millions and not billions of years, but with the emergence of language there was a further acceleration of time and the rate of change. William Irwin Thompson
The twentieth century was like twenty years' worth of change at today's rate of change. Ray Kurzweil
In most Western economies, the general relationship is not in fact between the rate of inflation and the level of unemployment, but between the rate of change of inflation and the rate of change of unemployment. Paul Ormerod
With the emergence of civilization, the rate of change shifted from hundreds of thousands of years to millennia. With the emergence of science as a way of knowing the universe, the rate of change shifted to centuries. William Irwin Thompson
The rate of change is not going to slow down anytime soon. If anything, competition in most industries will probably speed up even more in the next few decades. John Kotter
When the rate of change increases to the point that real time required to assimilate change exceeds the time in with change must be manifest, the enterprise is going to find itself in deep yogurt. John Zachman