Answer: Those who are better off economically are likely to have advantages of better living standards.
Explanation: With better living standards, upper economic classes have more acess to education, health systems, better jobs, etc. In this way, the least advantaged classes, that have difficult or no acess at all to such services, are at lose. Without education, the jobs are worse and worse. Being not able to have a well-paid job, a person can't afford health services, therefore resulting in higher death rates among them. That is the idea behind the "social inequality of death" theory.