It'd be interesting to see if reversal of the Flynn effect is correlated with massive unskilled immigration (esp from third world countries), which has accelerated in many European countries.

If we examine countries with extremely strict immigration policies that favor the skilled (e.g. Singapore), will we see IQs going up?

The concept of IQ-shredder is also relevant: http://www.xenosystems.net/iq-shredders/