I too would be interested in sources for this assertion. It goes contrary to what I would say if I were asked to guess about classes of today compared to classes of fifty years ago.
edit: Oops, I should have refreshed page before commenting, as I now see Vladimir_M responded. Leaving comment for content about my state of mind on this issue.
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: