The reason for this pluralism is that countries differ in how many % a parties must at least get to have any seats. Most countries impose an artificial limit, called election threshold. Netherlands does not.
Can Europe learn from Ghana? Buried on Wikipedia is a 3 sentence part about how Ghana deported 20% of the population -- 3 million people -- all the non-Ghanans. And it only took 3 months. The "Ghana Aliens Compliance Order" (GACO)
This website provides the history. It begins, of course, with economic migration since Ghana was the gold coast. In fact, these migrants were going into a British colony, probably for the usual reasons of wanting to live under European domain: rule of lawand prosperity.
European rule eventually declined, and just after they left (1957), the economy goes bad. At least, so they say, but it doesn't look that way until 1970s by GDP stats.
In Germany, non-German students (anyone with "migration background") get lower grades and test scores.
Due to their politics, teachers are expected to have some bias towards girls, minorities, low-SES etc. students. So do they? The authors find that, yes, they do.
New Dutch results on immigration. Sobering as usual. There are 3.7 million foreigners in the Netherlands.
One can calculate a given person's contribution to the state budget by adding up all their contributions (revenue) and subtracting all of their costs. Doing so gives a net contribution metric. Dutch people are c. net 0, and the others groups net negatives.
There's a lot of variation though. Numbers for the first generation can be very positive or negative. It's easier to get very positive values because many people arrive after having finished their education, so begin working immediately. Many of them leave before pension too.
Many of you have seen this figure. A pessimist's favorite. A massive innovation decline starting from 1880 or so.
It fits suspiciously well with the onset of dysgenic fertility in NW Europe, or at least the UK.
However, does this really work this way? It's based on a 2004 book called The History of Science and Technology that recorded significant events from 3000 BC to 2003 or so. But what if the author missed newer stuff that wasn't recognized as important yet?