If we plot a wealth indicator and the number of granted patents, there should be shown some correlation. In the following graph, the number of Dutch granted patents was plotted against the GDP per capita (in international 2005 dollars) in the Netherlands .
Well not much to our surprise, there is indeed a nice correlation.... and the along the data points, neatly, the time evolves from 1800 in the utmost lefthand side lower corner to 2012, in the utmost righthand side upper corner.
Some strange things happen, e.g. in 1978, when the first European patents granted with effect for the Netherlands came to live. The number of patents increased massively, whereas the growth in GDP per capita didn't. Actually, in the late 70ties and early 80ties there was a quite severe economic downturn.
from 1800 till 1979 there was a very steep correlation between the number of patents granted and the growth of wealth in the Netherlands. One important factor in this is, much to my believe, the very strict granting policy of the former Dutch patent authority, de Octrooiraad.
In the 90ties, we see even a decade of reversed correlation, the number of patents granted for the netherlands decreased, whereas economy was booming. This effect is greatly due to the backlog building up at the premises of the European Patent Office, suffering from their enormous success.
In the last decade, there appears to be again a decoupling of our economic fitness and the number of patents granted. Here again, it appears that though inventive power is extreme, economy is not (yet) picking up. To my opinion, the rise in patents granted will most certainly boost economy in the near future, such that the correlation is regained.
One remark though, a correlation is different from a causality. Correlation is relative easy to proof, causality is a lot more difficult. This being said, I do conclude, yet again, that patents do contribute to prosperity!
It is simply to difficult to ignore...
 Gap Minder: http://www.gapminder.org/data/ Data on GDP/cap in PPP US$ 2005: Gross Domestic Product per capita by Purchasing Power Parities (in international dollars, fixed 2005 prices). The inflation and differences in the cost of living between countries has been taken into account.