Banca d'Italia research paper No. 159, "Basel 2.5: potential benefits and unintended consequences" (April 2013) by Giovanni Pepe looks at the Basel III framework from the risk-weighting perspective. Under previous Basel rules, since 1996, "…the Basel risk-weighting regime has been based on the distinction between the trading and the
banking book. For a long time credit items have been weighted less strictly if held in the trading book, on the assumption that they are easy to hedge or sell."
Alas, the assumption of lower liquidity risks associated with assets held on trading book proved to be rather faulty. "The Great Financial Crisis made evident that banks declared a trading intent on positions that proved difficult or impossible to sell quickly. The Basel 2.5 package was developed in 2009 to better align trading and banking books’ capital treatments." Yet, the question remains as to whether the Basel 2.5 response is adequate to properly realign risk pricing for liquidity risk, relating to assets held on trading book.
"Working on a number of hypothetical portfolios [the study shows] that the new rules fell short of reaching their target and instead merely reversed the incentives. A model bank can now achieve a material capital saving by allocating its credit securities to the banking book [as opposed to the trading book], irrespective of its real intention or capability of holding them until maturity. The advantage of doing so is particularly pronounced when the incremental investment increases the concentration profile of the trading book, as usually happens for exposures towards banks’ home government. Moreover, in these cases trading book requirements are exposed to powerful cliff-edge
effects triggered by rating changes."
In the nutshell, Basel 2.5 fails to get the poor quality assets risks properly priced and instead created incentives for the banks to shift such assets to the different section of the balance sheet. The impact of this is to superficially inflate values of sovereign debt (by reducing risk-weighted capital requirements on these assets). Added effect of this is that Basel 2.5 inadvertently increases the risk of sovereign-bank-sovereign contagion cycle.
The paper is available at: http://www.bancaditalia.it/pubblicazioni/econo/quest_ecofin_2/qef159/QEF_159.pdf