"Third world" is really not a great term for these kind of discussions, it's a cold war relic. In the 'true' sense of this term, Ireland, India, Nigeria (and Sweden!) were third world countries, because they were aligned with neither NATO nor the Warsaw Pact, while Spain, Italy, Poland and Romania were not.

Somewhere along the line this term was misunderstood and repurposed into a euphemism for "underdeveloped" or worse, with racial undertones. Best to just drop the term from your vocabulary unless you're talking about the cold war.