Happiness and work in Ireland

One of the results that emerged from the well known Whitehall studies, considered landmark studies in social epidemiology which looked at British civil servants, is that where people come in an organization has an important effect on people's health. People at the bottom of the rung had poorer health. One explanation is that such people have less control of their circumstances and have more stress as a result.
The European Social Survey asks individuals how much control they have over how their daily work is organized (on a scale of 0 to 10). As an alternative to looking at health, one could also consider subjective well-being: in the data happiness is also ranked on a scale of 0 to 10.
The graph plots the mean of the happiness variable against how much control individuals say they have, using the data for Ireland. This is purely a bivariate comparison.
So there is a correlation with those at the top recording greater happiness but the gradient seems fairly gentle to me. More importantly, those at the bottom of the ladder seem happier than those immediately above them. So it may be that those at the bottom just don't worry and get on with things. A multivariate analysis would be needed to consider this more throughly.
If one looks at subjective general health with the same data, the relationship is rather more monotonic with those at the top having better health.