Inflation that is sudden or unexpected tends to hurt which of these groups of people most?

The answer is people with fixed income. Inflation is a danger factor that certainly affects all investments. It's particularly magnified with fixed income ones. Inflation is the slow and refined erosion of the buying power of your dollars over a period of time. Fixed income investments pay a stable amount of dollars of interest and give back a set amount of dollars of principle at the future. The buying power of those dollars reduce each and every year that passes. So, while you're receiving the same number of dollars, you're not capable to buy the same quantity of goods and services with them.