It is absolutely true fact that, especially in developed countries, young people are being richer, healthier and enjoy extended lifespans. However people with this improvements do not fell happier. I would state that this problem has one main reason why increased wealth and well-being do not necessarily translate into greater happiness.
One of the significant reason why increased wealth and well-being do not always leads to being unhappy is the growing pressure from different success and maintain high standards. I think in many developed countries the pursuit of the success comes with heightened hopes and stress. When young people have financial stability in their work and better healthy they are frequently find competitive environment where people comparing themselves to their peers. This event lead young people to strive relentlessly and to be perfect in their life because of this situation young generation feel anxiety and deficiency in their themselves. As individuals strive this thing set by society they may lose sight of what truly brings personal fulfillment and joy, result increased materials achievements but reduced to being happy.
To solve this issue of decreased happiness despite growing health wealth and others people should be these activities. These are young generation reduced to comparing their own lives among their peers, during learn something new they are less anxiety, so learn with easy going mood and approach. As a result the actions mentioned above will 100 percent lead you to happiness.
In conclusion that different in developed countries have people which they have money but not happiness. I think it is depend every person how to being happy in your life.