Does sun make you unhappy?

Does sun make you unhappy?

On 24^th of April a newsarticle was published on a Belgian website reporting about a study among people who migrated to the south of Europe from northern countries. 

According to this news item, 300 people who migrated from Belgium, The Netherlands, Germany, the UK, France and Switzerland to a Mediterranean country were included in the study. When asked how happy they were, measured on a scale with 10 as maximum, these expats scored themselves with an average of 7.3. In a study among 56,000 people in Northern-Europe, the average score on this scale was 7.5.

Does these results justify the head of the article: “Verhuizen naar de zon maakt niet gelukkiger” [Moving towards sunnier place does not make you happier, your cow]?

What could it mean?

The news article presents a comment of a sociologist, involved in the research. His hypothesis about this assumed unhappiness is that moving can disturb social lives. That is off course a possibility, but there is (at least) one other explanation: sampling bias.  

Sampling bias is a frequent problem in statistics. For instance: a lot of sociological studies are conducted by means of a survey. People are invited to participate in the study by filling in a question list that has to be sent back to the researchers. Even if the researchers try to ask a random sample of the population to fill in the forms, the people who actually do participate can be a selective group. A lot of people are simply not interested in or motivated for this kind of studies. The results from the study are then only applicable to this selected group of people, who might be quite different from the average person.

If you find this difficult to understand, try the following. Look at the figure in this article. Close your eyes and put your finger somewhere on the picture. Imagine that you can only observe that part of the picture at which you are pointing. What color is the pictures where you are pointing? As you can not observe other parts of the pictures, you may get the impression that the picture only has one color. The same happens if you are looking at a small part of the population. Researchers tend to assume that the people who did not participate in a study are similar to the people who do. Which can be a huge mistake.

Is this a one-colored picture?

In the case of the migrated people, a similar thing could have happened. For instance if only people who are already unhappy migrate. People who are completely satisfied with their live, will probably be less motivated to change anything. People who feel unhappy and hope that they can change that feeling by moving to an other country will be more motivated. The researchers who are studying the expats may well be looking at the unhappier part of the population. It is even possible that these people got indeed happier. Maybe they had an average happiness score of only 6.5 while living in their home countries. That could mean that these countries could have got more happy  on average because the unhappy people are leaving, while the unhappy people got more happy because they changed their lives.  

So don't worry if you are moving to the south, just go for it. Everyone will get more happy that way.