Or think of the issue of accounting standards: How complex is the system if it remains hard to compare the balance sheets of US banks with those of European banks? So, I believe that complexity is mainly caused by the multitude of approaches; not by a single regulatory step.
Notes: For each horizon, the chart shows the median of estimates of the lower quantile (10th percentile) forecast across the suite of “GDP-at-risk” models maintained by ECB staff, as well as the interquartile range to account for model uncertainty. These estimates are predicated mainly on developments in financial conditions, credit, risk, and the macroeconomy.