Forget the 35,000 people of Liechtenstein.
There are also small countries that do not have high GDP per capita in West Europe, and did not have that for more than a century.
Small countries can have many perks or little perks, A random effect.
Bigger countries have usually less bandwidth in perks.
Take Belgium, just after Napoleon the French speaking South part had the most important perks to get heavy industry developed and the higher GDP per capita there
With now heavy industry less important and trade more important the Flemish North part with the Port of Antwerpen has the better perk and has the higher GDP per capita there.
The two states added together as Belgium score that whole period 1800-2000 well though not excessive.
A good way to look at GDP is to look as well to the regions.
Here a map with GDP in PPS per capita per region of the EU
The "music" is basically along the old Hanseatic Spices Route from the Italian City States, along the Rhine to the Sea. The subroute is from the South of Germany to the gate of East Europe Vienna (near Prague, Bratislava, Budapest) and going to Timisoara-Sibiu-the Black Sea will emerge back over time as well as higher GDP area.. The other old route in South Poland the Silesia route to the East.
And do note, comparing 2004 and 2014, that the 2008 GFC and subsequent Eurocrisis had a differing effect on the regions. You always need to prepare for storms, but that cannot be by staying safe in your harbors. The defenses you build up in the good times must be both static (absorbing the blow) as dynamic (what to do now). How you come out of the storms counts !!! Because storms are inevitable.
And if getting back goes to slow the next storm will hit before you had your defenses up again.
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https://brilliantmaps.com/regional-eu-gdp/