Use case: ability to quickly see each category's amount spent as a percent of income for that month. If spending exceeds income, then the proportions would add up to over 100%. This would give an easy way to see how much of income is being spent on needs, wants, savings, etc.

Update needed: Add "Total income" option for "Show against" in Spending Breakdown section. Or an easy way to see a percent of income spending in each category.