If, for example, each of the two tenants had an income of $20,000 a year initially, and later both reach an income of $30,000 a year, leading to each living in a separate apartment afterwards, that will mean a fall in household income for these individuals from $40,000 a year to $30,000 a year. There will now be two low-income households instead of one, and each household will be poorer than the one they replaced. Again, a rise in individual income can be reflected statistically as a fall in household income.
