An interesting observation there Patrick. However, it raises a whole lot more questions than it answers.
First of all, which is the cause and which is the effect? There’s a massive difference between secularism causing prosperity and prosperity causing secularism. Don’t forget that prosperity brings complacency, and that could be just as large a factor as any.
Secondly, he talks about a correlation between secularism and happiness – but how do you measure happiness? If you’re trying to measure it in terms of healthcare provision, freedom of speech, average salaries, and all the rest of it, you could come up with a metric that proves anything you like. Especially if you threw antidepressant use or suicide rates into the mix, for example.
In any case, this is just one data point in one part of the world at one particular time in history. A more rigorous and scholarly analysis would need to conduct worldwide surveys over multiple generations, and even then it would most likely reveal a complex interplay between numerous different factors. You need to consider such things as the difference between state religions and minority religions, for example.
Basically, this is just the atheist equivalent of the YEC argument about the rate of change of the Earth’s magnetic field. Same fallacies, same cherry-picking, same rhetoric, demonstrating nothing at all.