The peace of the lobotomised or the peace of the contended?
That we’re getting better at not killing each other because of international trade co-dependence is a double edged sword. It brings a certain type of peace, but also eg economic sanctions which keep people incompetent. Peaceful, yes. Prosperous no.
Not having citizens protest in the streets because they’re resigned to its futility is peaceful, too. But passive hopelessnesss is not a precursor to prosperity.
We need to be careful what we measure. Number of premature deaths per capita is good, but once we’re below a certain threshold (and it is 2015 so we should be), other indicators tell us more, eg social mobility, enfranchisement, equality and equity, health, happiness, number of people with hobbies and so on.