Basel III, the Basel Committee on Banking Supervision's response to the 2007-09 financial crisis, raises minimum bank capital quality, adds a 2.5% capital conservation buffer, sets a 3% minimum leverage ratio, and introduces a Liquidity Coverage Ratio requiring banks to survive 30 days of liquidity stress.
How did the 2008 financial crisis expose gaps in bank oversight, and how did regulators respond?
The Basel Committee on Banking Supervision (BCBS) developed Basel III directly in response to the financial crisis of 2007-09, according to a Bank for International Settlements (BIS) page last updated in 2017CITE:E1. The US Federal Reserve, in a 2013 description of the framework, characterizes Basel III as "a comprehensive set of reform measures, developed by the BCBS, to strengthen the regulation, supervision, and risk management of the banking sector"CITE:E6. Both the BIS, the institution housing the BCBS, and the Federal Reserve, the US regulator implementing the standards, describe the package as a direct, internationally agreed response to the crisis rather than a routine periodic updateCITE:E1CITE:E6.
How does Basel III redefine bank capital requirements?
Basel III raises the minimum levels required for Common Equity Tier 1 (CET1), Tier 1, and total capital ratios, and improves the overall quality of capital banks must hold, according to a 2019 BIS Financial Stability Institute (FSI) summaryCITE:E2. The summary does not specify the new numerical ratio floors themselves, only that minimum levels across all three capital categories were raised and capital quality was improvedCITE:E2.
What is the capital conservation buffer, and why is it set at 2.5%?
The capital conservation buffer requires banks to hold additional capital equal to 2.5% of total risk-weighted assets, on top of minimum capital ratiosCITE:E3. The BIS states the buffer was implemented in full as of 2019CITE:E3.
What does the 3% minimum leverage ratio add beyond risk-weighted capital rules?
Basel III sets a minimum leverage ratio of 3%, a requirement calculated independently of risk-weighted assetsCITE:E4. Per the BIS's 2019 summary, this 3% floor was set to remain in place until the BCBS finalizes its calibration and any necessary adjustments to the exposure-measure definition, with a view to migrating the ratio to Pillar 1 treatment on 1 January 2018CITE:E4.
How does the Liquidity Coverage Ratio ensure banks can survive a 30-day stress period?
The Liquidity Coverage Ratio (LCR) requires banks to hold a sufficient reserve of high-quality liquid assets (HQLA) to survive a period of significant liquidity stress lasting 30 calendar days, according to the BIS's 2019 FSI summaryCITE:E5.
Basel III's quantitative thresholds at a glance
| Requirement | Threshold | Timing |
|---|
| Capital conservation buffer | 2.5% of total risk-weighted assets | Fully implemented as of 2019CITE:E3 |
| Minimum leverage ratio | 3% | Set to migrate to Pillar 1 treatment on 1 January 2018CITE:E4 |
| LCR stress survival window | 30 calendar days of HQLA coverage | Per 2019 BIS summaryCITE:E5 |
Taken together, the record shows a layered structure built over more than a decade: the BCBS began developing Basel III in direct response to the 2007-09 crisisCITE:E1, the Federal Reserve was already describing it as a comprehensive reform package by 2013CITE:E6, and by 2019 the BIS's own summaries confirm that the capital conservation buffer had reached full implementation at 2.5% of risk-weighted assetsCITE:E3, alongside a 3% leverage floor originally tied to a 1 January 2018 migration targetCITE:E4 and a 30-day LCR liquidity-survival standardCITE:E5. The consistency between how the BIS and the Federal Reserve each describe the same framework, across sources published six years apart, indicates the capital, buffer, leverage, and liquidity elements were designed and rolled out as one coordinated package rather than as separate, unrelated rules.
Author's Take・EffectStory 編輯部
The structure here is telling: instead of pushing one dial harder, the BCBS paired higher-quality CET1/Tier 1/total capital ratios with a leverage ratio that ignores risk weighting entirely, plus a 2.5% conservation buffer and a 30-day LCR — four independent constraints rather than one reinforced rule. That design choice implicitly treats risk-weighted capital measures as insufficient on their own, since a non-risk-weighted 3% floor only makes sense as a backstop against models that can be gamed or miscalibrated. The multi-year rollout also matters: the BCBS started this work in response to the 2007-09 crisis, the Federal Reserve was already calling it comprehensive by 2013, and the capital buffer only reached full implementation in 2019 — a decade-plus build-out, not an emergency patch. The concrete thing to track going forward is whether the leverage ratio's calibration, which the BIS said was still pending finalization as of its migration target of 1 January 2018, has since been locked into a permanent Pillar 1 form.