Golden Age? How Can We Tell?

This article from The Guardian suggests that "We are right in the thick of a golden age of children's literature." But why? Other than that I'm publishing kidlit now, of course?

A little discussion of this article took place at Child_Lit where the question of how to determine a golden age came up a few times. Is the fact that specific titles are selling in large numbers, as The Guardian tells us, an indicator that we are in a golden age? Do adults reading kids' books mean we're in a golden age? The fact that publishers will spend a lot of money promoting a few big name kidlit authors--is that enough to prove we're in a golden age?

Probably the quality of the writing should be the biggest factor in labeling a period a golden age of writing. But has their ever been a period when a writing community didn't believe that its writers were doing fine work?

I wonder if an assessment of a point in time can best be made after that point in time is over. Those who come after us will need to decide how golden our time was.