There's a persistant meme that greater income has no impact on happiness. I see this brought up most frequently in conversations about international development – should we really view economic development in China or India as a positive thing? Will it really lead to greater happiness there? The data says, without a doubt: Yes.
Betsey Stevenson and Justin Wolfers, surveying happiness data in dozens of countries over the past decade, have found a clear correlation between the log of income and how satisfied with life people say they are, that holds true inside nations and between nations.
To be clear, other factors – health, social connections, marital or relationship status, genetics – play large roles and often quite larger than income. And many wealthy people are miserable. How you use money, and the other circumstances of ones life matter. But income is a significant factor. Particularly at the low end, where a very small absolute change is a large percentage change in income, that's reason to hope for economic growth.