Being poor comes with many inadvertent costs, while being rich comes with unexpected benefits. For example, poor people are more likely to be in ill health and have poor dental hygiene, which may cost more money in the long run. In contrast, wealthy people can afford to spend money to maintain their ideal level of fitness.

A recent article published in Royal Society Open Science analyzes another advantage the rich have over the poor: wealthy people are able to sleep until later in the morning. In essence, the rich buy the ability to rest more and commute more efficiently.

The paper in question uses data from human mobility studies, which examine large data sets of human movements in search of patterns at particular times of the day or year. This study uses survey response data from the Colombian cities of Manizales and Medellin. The authors separate their population into six different socioeconomic strata to look at finely tuned differences in economic status. This is possible because, in Colombia, households are legally assigned to a different economic strata according to their physical and environmental characteristics. The Colombian government does this for the purposes of differential public services fees.

Next, the researchers examine the mobility network for each socioeconomic class. These mobility networks are diagrams of people's movements within their cities. The researchers find that the network for each socioeconomic strata show different structural properties. The most densely populated classes, which tend to be middle class, show more densely connected mobility networks, with people interacting with each other more regularly in their daily movement patterns. Middle-income travelers also tend to use multiple modes of transportation, including public transit and some private options.

In contrast, the lowest classes and the highest classes both have large movement path lengths, meaning that people in these classes travel longer distances every day. However, those in the highest socioeconomic strata tend to travel only within a few zones of the city, mostly in high-cost modes of transit, like personal vehicles or cars driven by others. In comparison, those in the lowest socioeconomic strata tend to disperse throughout the city via irregular routes, likely due to dependence on walking or public transit.

In addition to these spatial patterns, the authors are also interested in temporal patterns. So they look at the times of day when people in the different groups are likely to travel. The researchers were surprised to find that the timing of movement is also closely linked to socioeconomic status. They saw that as socioeconomic class increases, every morning's peak transit time moved to later and later in the day. So people with the lowest status had peak morning transit times around 5AM or 6AM, whereas those with higher incomes didn’t peak until nearly 7AM.

The authors conclude that higher socioeconomic status allows people to buy more time to sleep or engage in leisure activities in the morning, so they can leave their homes later. In contrast, people with less economic capital tend to leave their homes earlier because they utilize slower and less reliable modes of transit, such as walking or taking public buses.

Though this study was meant to probe the importance of socioeconomic status in human mobility, it also shows another important point: wealth allows people to buy a more comfortable life. This is sobering because it suggests that possessing wealth is a self-perpetuating state. The poor, who spend more time stuck in transit, have less opportunity to increase their income. The poor may also be unable to afford the luxury of sufficient sleep, which influences their ability to pull themselves out of poverty.

One obvious solution for the poor is to provide them with more efficient and affordable transit. If poor people could afford some of the time-related benefits that the wealthy are able to buy, perhaps they would be better able to gain a foothold in a higher socioeconomic stratum.

Royal Society Open Science, 2016. DOI: 10.1098/rsos.150654 (About DOIs).