How would you quantify 'extent'?

I recently submitted my EPQ project proposal to my supervisor who read it and offered one suggestion: quantify 'extent' in the title. My current title is as follows:

'To what extent is the intellectual, social and emotional development of infant school military children affected by their parents’ service in the Royal Air Force?'

This question will be answered in the form of a 5000 word essay and therefore I want to structure it as a discussion (hence 'extent', rather than an objective yes or no. However, the phrasing still needs to be modified and quantified. What would you suggest? Thanks!