Why does happiness matter? There are countless reasons why, but one strong economic reason is because happy people are productive people.
And productivity is crucial for a country emerging from a deep recession.
Happiness is an appropriate measure of national wealth, not a concept to be dismissed as touchy-feely.
By measuring happiness, we're measuring mood and people's ability to deal positively with challenges and what life throws up.
So it's worrying to learn that the mood of the nation is lower this winter than last.
Research commissioned by Turning Point (based on a sample of 2040 UK adults) shows that more than a quarter of Britons are feeling worse than before.
The survey also reveals that a significant number of people are coping by pretending to be ok rather than seek support.
The Government has made parity of esteem between physical and mental health a legal obligation in the NHS.
That should mean that resources in mental health are allocated in proportion to need just as they are for physical health problems.
Yet spending on mental health has been cut while referrals to crisis and community mental health teams are rising.
It seems blindingly obvious to say that the Francis report applies to the NHS as a whole, not just the acute sector.
Parity of esteem does not mean equal funding pound for pound for mental health but it does mean equality of consideration and fair funding.
Then there's the impact of welfare reforms on the 'mood' of those on the margins.
Organisations like Turning Point know that welfare reforms are causing deep unhappiness.
Mental health trusts have seen numbers rise as a direct result of the anxiety and fear that benefit caps and the bedroom tax have induced in people.
We've had at least two strategies on mental health launched by this Government and the last.
Then there was Nick Clegg's mental health action plan launched last month. It's wonderful rhetoric, and no doubt the deputy prime minister means it when he says that it's 'just plain wrong' to treat mental illness as the 'poor cousin' of physical health in the NHS.
Let's hope his statement doesn't get filed away and forgotten because there is a desperate need for easy-access, non-stigmatising services.
And we've also got a new agreement between police and the NHS to improve mental health crisis care. The Crisis Care Concordat is aimed at driving up care standards for people experiencing crisis and to stop so many ending up in police cells.
It's crucial for other taxpayer-funded services- the police, education- to be clued up about mental health. Not just the NHS.
We need proper data on how much is being spent on mental health. Otherwise, it will be difficult to know if we're achieving parity of esteem and to hold managers to account. We also need to be clear on what we mean by parity of esteem and the priorities we have to deliver on. And one of those priorities is happiness. According to the latest UK happiness index, the average Briton rates their 'life satisfaction' as 7.4 out of ten. That figure needs to be put into context though. I doubt many young people who have been hammered by the recession are happy.
This takes me back to why individual happiness is important for the prosperity of the nation. After all, it was an economist, Lord Richard Layard, who designed the most significant programme this century for delivering large scale mental health support. His work on happiness led to the setting up of Improving Access to Psychological Therapies (IAPT) to help people suffering from depression and anxiety.
Lord Layard could clearly see the obvious truth that happy people are more productive. I believe that investment in IAPT needs to continue. But the programme could stall if we don't achieve parity of esteem, if investment is undermined.
Doing a survey to rate the nation's mood is fine in principle but all it does is show us how far we have to go.
What politicians need to show is what they've done about the results in policy terms.
Otherwise handing out happiness scores is a pointless exercise.