jmc

Notice that in two of the increases, the dollar amount doubles. The increases in which this is not true is $2$ to $3$, $3$ to $4$, and $11$ to $12$. We can disregard $11$ to $12$ since that increase is almost $2$ times. The increase from $2$ to $3$ is $\frac{300-200}{200}=\frac{1}{2}$, so it's only multiplied by a factor of $1.5$. The increase from $3$ to $4$ is $\frac{500-300}{300}=\frac{2}{3}$, so it is multiplied by a factor of $1.\bar{6}$. Therefore, the smallest percent increase is $\text{From 2 to 3},\boxed{\text{From 2 to 3}}$