New research by Harvey James found that happier people tend to be more ethical:
I found a correlation between how people responded to ethics questions and their satisfaction with life. As part of the 2005-06 wave of the World Values Survey (which examines attitudes around the globe), respondents were asked in face-to-face interviews: On a scale of 1 to 10, how satisfied are you with your life? There were also four ethics questions that ask how acceptable or unacceptable they felt a particular practice is: claiming government benefits to which you are not entitled; avoiding paying your fare on public transportation; cheating on taxes; and accepting a bribe. What I found is, generally, people who believe that these particular ethical scenarios are not acceptable also tend to indicate they are more satisfied with life. That’s with controlling for other factors that scholars have shown are also correlated with happiness, including relative wealth.