The first accord was the Basel I. It was issued in 1988 and focused mainly on credit risk by creating a bank asset classification system. This classification system grouped a bank's assets into five risk categories:
0% - cash, central bank and government debt and any OECD government debt
0%, 10%, 20% or 50% - public sector debt
20% - development bank debt, OECD bank debt, OECD securities firm debt, non-OECD bank debt (under one year maturity) and non-OECD public sector debt, cash in collection
50% - residential mortgages
100% - private sector debt, non-OECD bank debt (maturity over a year), real estate, plant and equipment, capital instruments issued at other banks
The bank must maintain capital (Tier 1 and Tier 2) equal to at least 8% of its risk-weighted assets. For example, if a bank has risk-weighted assets of $100 million, it is required to maintain capital of at least $8 million.