I completely disagree with your premise. Can you cite any evidence of the claim that parents are "healthier, smarter and wealthier" than people who will not have children? In my experience the decision to have children is often not even a decision at all and is just something that happens.
The question is also not "whether things have gotten harder for the average person". The article clearly states:
"Economists and sociologists from Stanford, Harvard and the University of California set out to measure the strength of what they define as the American Dream[1], and found the dream was fading. They identified the income of 30-year-olds starting in 1970, using tax and census data, and compared it with the earnings of their parents when they were about the same age."
The question is the viability of an American dream based on opportunity for children exceeding that of their parents.
From the article:
“My parents thought that one thing about America is that their kids could do better than they were able to do,” said Raj Chetty, a prominent Stanford University economist who emigrated from India at age 9 and is part of the research team. “That was important in my parents’ decision to come here.”
The question is also not "whether things have gotten harder for the average person". The article clearly states:
"Economists and sociologists from Stanford, Harvard and the University of California set out to measure the strength of what they define as the American Dream[1], and found the dream was fading. They identified the income of 30-year-olds starting in 1970, using tax and census data, and compared it with the earnings of their parents when they were about the same age."
The question is the viability of an American dream based on opportunity for children exceeding that of their parents.
From the article:
“My parents thought that one thing about America is that their kids could do better than they were able to do,” said Raj Chetty, a prominent Stanford University economist who emigrated from India at age 9 and is part of the research team. “That was important in my parents’ decision to come here.”
[1]: http://www.equality-of-opportunity.org/