Rates vs Percentage

#1
What is the rule of thumb for when to report a rate vs. a percentage? For example, if you want to show trends from year to year in the rate/percentage of people in the population who get cancer, a trend using percentages (number of people who get cancer/number of people in population) will be identical to a trend using rates (same division but multiply by 1,000 or whatever "per" group you want to use). Are rates ever more "accurate" in some situations, or do they just express the same amount in a different way?
 

Mean Joe

TS Contributor
#2
I'm pretty sure they express the same amount, just in a different way. It seems like if the percent is less than 0.1, then a rate (per 100,000) is used. Cancer is usually expressed as a rate (14 per 100,000), because the percent is so small (.014%). The confusing thing about seeing a percent like this, is that I start to worry "Am I supposed to move the decimal over two more places?"