And what this chart only begins to hint at is that these high rates have been sustained for a long period, and are unlikely to return to normal levels anytime soon.

He found that in recessions that followed financial crises, growth was a lot slower and credit growth stagnated-whereas after normal recessions it soared (see chart 6).

The primary research shows that the evolution process of requirements can be regarded as normal when the requirements evolutionary process changing chart is consistent with the model trajectory.