# A test for exponential growth

Actually, its very useful that only exponential growth gets straightened out by log transformation. Now we have a **quick-and-easy test to find out if a population is undergoing expontial growth**. Namely

- Plot the population on log paper.
- Decide if the trajectory forms a straight line.

That's pretty much it!! A straight line on graph paper means exponential growth (if the line goes up) or exponential shrinkage / death (if the line goes down). If the line is straight but completely flat, it means no change, just like on a regular graph.

So, looking at the graph below...

When was the population growing exponentially? (rollover over the graph for a clue)

When was the growth slowing down?

When was the population constant?

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