I am confused by this fact since I arrived to the United States. Let's see a sample sentence to exemplify the doubt. If I don't recall it erroneously, according to my English books, the phrase
"the amount represented a 9% of the Gross Domestic Product of the country"
could be rephrased as
"the amount represented a 9% of the country's Gross Domestic Product"
However it doesn't sound unfamiliar to me to see this same last structure but without the apostrophed s
"the amount represented a 9% of the country Gross Domestic Product"
I don't know if this is simply part of a more informal register, or if indeed it is accepted in American English