To be fair, he said 30% higher which would be correct. Let's bear in mind that the GDP also registers prisons expenditures, weapon manufacturing and the cleanup of car accidents as positives.
A higher Gini index means a greater inequality; to add insult to injury, social mobility is also larger in the Nordic countries. Rags to riches happens almost twice as often in Denmark.
Running an efficient free market requires heavy government intervention, paradoxically.
For DF, I think the most practical solution would be to balance demands with a market system, keeping supply under the player's control. That's more or less how it is now, but with prices of labour and goods under player control. The dwarves would then buy what they like (and it's best to let them buy and place their furniture too), and if something is lacking they would go to the relevant guildmaster and request it. Those guildmasters then give you a nice report about the needs of the community.
Additionally, keep a marketplace where foreign merchants can sell their goods privately. These would be only consumer goods; the raw materials trade would remain under player control (including semi-finished products like cloth).