To determine which region showed the highest growth in the number of households in all income categories, we need to consider the percentage growth in each region for the three categories (middle income, upper-middle income, and high income).
From the bar chart, we can see that South has the highest percentage growth in all three categories:
- For the middle income category, the growth is over 300%.
- For the upper-middle income category, the growth is also the highest in South.
- For the high income category, South again has the highest growth.
Thus, the correct answer is South.