pluperfect subjunctive v past perfect in this sentence
In an article about certain Latin American countries winning awards from the United Nations for their demilitarization policies, there is the following sentence:
En 2013, el foco de este premio fue resaltar las políticas de desarme que hubieran contribuido a la paz, al desarrollo sustentable y a la seguridad.
If I were to write that sentence I would probably say "habían contribuido" rather than "hubieran contribuido." I don't understand why the pluperfect subjunctive was used.
2 Answers
The feeling in Spanish is that the focus of the award was to highlight the policies of disarmament that might/may have contributed to peace, sustainable development and safety. The inference is that probably not all of the policies made that contribution. They may have and might have not.
Although I agree with Daniela that the subjunctive can be used to mean 'might or may'/ 'might have, may have' etc but I dont think that it's necessarily the case in this example (I am not however a grammarian and this is just my opinion).
This isn't the easiest thing to explain but when you form a Spanish sentence with (for example) 2 clauses I believe you can use the subjunctive in the second clause to purely avoid declaring that information. It's good for adding some relevant information which isn't your focus but is still helpful, or for avoiding re-declaring information that is already known to your hearers/readers etc.
Indicative - used to 'declare' facts (or things that you believe to be a fact).
En 2013, el foco de este premio fue resaltar las políticas de desarme
In 2013, the focus of this award was to highlight the disarmament policies
... this is the main point that you want to share (indicative)
Subjunctive used for everything else, often just to relegate certain information to a less important level, not necessarily to cast doubts on its veracity etc
que hubieran contribuido a la paz, al desarrollo sustentable y a la seguridad.
that had contributed to peace, sustainable development and security.
... I would also consider this to also true but to be information of secondary importance from the speaker's viewpoint.
It would sound incorrect to me to use 'habían' but perhaps a native speaker will weigh in on that point.
If you're struggling to get your head around this you've probably seen this kind of thing in action with sentences that perhaps express emotion?
Eg. How would you translate this in Spanish?
I was happy that they had come to the party?
Likely you would use the indicative for the first clause and the subjunctive for the second clause, even though the second clause is also true.
So to use the same reasoning as I gave above ... the important part that you want to declare is how you felt, the second part is just as true but is relegated to a position of secondary importance by the use of the subjunctive.
I hope I haven't confused you even more. 
