The really important thing this touches on, IMO, is that people who are "poor," are not just cash poor or asset-poor, but also time-poor, and as a result they are increasingly sleep-poor. Because a unit of a poor person's time is worth very little money, they have to sell so much of it just to pay the bills, that it encroaches upon the time they have available for sleep. Being sleep-deprived drains a person's energy, causing them to work less efficiently, which helps perpetuate the vicious cycle of poverty.