[pantalaimon]

Is there a minimum quorum a party has to reach before they can enter parliament?

In Germany they need to get at least 5% of the votes. This was introduced because many small parties had made the parliament of the Weimar Republik unstable.

[captaincrowbar]

When New Zealand went shopping for a new electoral system in the 1990s, we ended up with one based closely on the German model, including the 5% threshold. The Israeli parliament was frequently pointed to as an Awful Warning of what would happen if we din't have the threshold.

[lambertsimnel]

Until 1992, Israel had a threshold of only 1%. Since then it has been repeatedly increased, and is now 3.25%. The parliamentary assembly of the Council of Europe (CoE) recommends such thresholds be no more than 3%. [0] (Many member states defy this recommendation. Israel is considered non-European for the CoE's purposes, and therefore isn't a member state, but it is an observer. New Zealand is neither a member state nor an observer, but it does participate in some CoE conventions.)

The aforementioned thresholds are "formal" thresholds, but there are also "effective" thresholds, arising from district magnitude. In the absence of a single "at-large" (nationwide, in this context) district, districts need to be large to bring the effective threshold down even to 5%. (It depends on the seat-allocation method, but it could be about twenty representatives per district for a 5% effective threshold, and over thirty for a 3% effective threshold.)

Where the effective threshold is higher than the formal threshold, the latter has no effect. But where a parliament has districts with different numbers of representatives, districts can have different effective thresholds, so any formal threshold could have an effect in some districts and not in others. I believe this is the case in Czechia, Poland and Turkey (but I don't know whether the formal thresholds there apply nationally or at district level). On the other hand, the Netherlands has no formal threshold and a uniform effective threshold of only 0.67%. The effective threshold of Israel's Knesset would be less than 1%, but still greater than the Netherlands'.

[0] "58. In well-established democracies, there should be no thresholds higher than 3% during the parliamentary elections. It should thus be possible to express a maximum number of opinions. Excluding numerous groups of people from the right to be represented is detrimental to a democratic system. In well-established democracies, a balance has to be found between fair representation of views in the community and effectiveness in parliament and government." http://assembly.coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fil...