The answer to the question of what makes the difference in categorizing these different levels of country development is “PRODUCTION”. First World countries produce more on a per capita basis than do Developing, or Third World Countries.
Production generates the necessary tax revenue base to support the other aspects of the “social good” of Society, such as better infrastructure and higher levels of education, to raise the level of development of a country, ultimately to a First World status.
The elevation through the various categories from Third World to First World status generally occurs by reason of a gradual socialization of the population into a more productive work-ethic through education. An important element for this transition to occur is a national pride instilled in the population by strong and honest political leaders, geared toward making members of a society more productive as individuals.
At the moment, I would categorize Costa Rica as a Developing Country. Although infrastructure meets a supportable level of development and basic public education is better than neighbouring countries, both still lag behind the standards set in First World Countries.
A stronger and more productive work-ethic will only develop with both a better public education system (having teachers who are able to teach) and the strong and honest leadership of the Country by politicians, who indeed put the welfare of the Country first above that of themselves, their family, and their friends.
A trait that I have noticed, existing particularly amongst professionals, Government employees, and the politically connected, which I consider to be damaging toward the development of the Country to a First World status, is a level of arrogance and a jealousy for the success of their peers, manifested most commonly by the general “stone-walling” and “obstructionism” in decision-making by those groups in Society.
Only when a strong national pride is instilled in the population as a whole, of wanting the Country to progress to the First World category of development, will such be achieved.