How do the various EU countries determine the length of Schengen visa validity?

I travel to the EU about once a year/every two years. I've applied for the Schengen visa thrice now - once for travel to Portugal, once to Greece, and most recently to Spain.
The Porgtuese consulate gave a visa that was valid for 10 days (my itinerary was 9 days long). For the same length of travel, different year, Greece approved a visa that was valid for 6 months. The most recent application for upcoming travel was at the Spanish consulate. They have approved a visa for 1 month.
A friend of mine applied earlier this year, at the Netherlands consulate, and he got a visa that was valid for 1 year.
In case you were wondering: I don't think it is finance: I have shown at every application that I could support myself for more than 6 months if I really had to (I only travel for a week or so at a time, and only for tourism purposes). I don't think it is ties to my home country either. I live in the US, own my place here, and have no itentions of moving to the EU. I prove that during my application as well. I have travelled around the world and have stamps from Singapore, Canada, the 3 visas above, and more.
Best Answer
In addition to the answer by Henning, there is a tendency to give the first visa for just the necessary duration of stay, with a few extra days of validity so that the visitor can shift (but not extend) the trip a little.
The second visa is given with more flexibility, since the visitor has shown that he was following the rules the first time around. After a couple more, there will be a multi-year, multiple-entry visa. A stable financial situation also helps to secure a longer visa.
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Do you know how long your Schengen Visa is valid for?
The duration of stay within the Schengen Area is always 90 days for the type C Schengen visa, but the validity of the Schengen visa itself may change. For double or multiple entry (circulation visa) Schengen visas, the validity of the visa ranges from 6 months to 5 years.How are Schengen dates calculated?
The 180-day period keeps rolling. Therefore, anytime you wish to enter the Schengen, you just have to count backwards the last 180 days, and see if you have been present in the Schengen for more than 90 days throughout that period.How does the Schengen 90 days in 180 work?
You can stay 90 days in any 180-day period within the Schengen area. calculated individually for each of these states. For instance, after a 90-day stay in the Schengen area, the person can immediately travel to Croatia and stay for another 90 days there. The 180-day reference period is not fixed.What does duration of stay in Schengen Visa mean?
The Schengen visa is a short stay visa and takes the form of a sticker affixed to the travel document. The definition of \u201cshort stay\u201d is a stay of "90 days in any 180 days period". This means that the total duration of stay is of maximum 90 days, in any period of 180 days.Schengen Visa Length of Validity (Europe Visa)
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