A capital requirement (also known as regulatory capital, capital adequacy or capital base) is the amount of capital a bank or other financial institution has to have as required by its financial regulator. This is usually expressed as a capital adequacy ratio of equity as a percentage of risk-weighted assets. These requirements are put into place to ensure that these institutions do not take on excess leverage and risk becoming insolvent. Capital requirements govern the ratio of equity to debt, recorded on the liabilities and equity side of a firm's balance sheet. They should not be confused with reserve requirements, which govern the assets side of a bank's balance sheet—in particular, the proportion of its assets it must hold in cash or highly-liquid assets. Capital is a source of funds not a use of funds. Regulations A key part of bank regulation is to make sure that firms operating in the industry are prudently managed. The aim is to protect the firms themselves, their customers, the government (which is liable for the cost of deposit insurance in the event of a bank failure) and the economy, by establishing rules to make sure that these institutions hold enough capital to ensure continuation of a safe and efficient market and are able to withstand any foreseeable problems. The main international effort to establish rules around capital requirements has been the Basel Accords, published by the Basel Committee on Banking Supervision housed at the Bank for International Settlements. This sets a framework on how banks and depository institutions must calculate their capital. After obtaining the capital ratios, the bank capital adequacy can be assessed and regulated. In 1988, the Committee decided to introduce a capital measurement system commonly referred to as Basel I. In June 2004 this framework was replaced by a significantly more complex capital adequacy framework commonly known as Basel II. Following the financial crisis of 2007–08, Basel II was replaced by Basel III, which will be gradually phased in between 2013 and 2019. Another term commonly used in the context of the frameworks is economic capital, which can be thought of as the capital level bank shareholders would choose in the absence of capital regulation. For a detailed study on the differences between these two definitions of capital, refer to Economic and Regulatory Capital in Banking: What is the Difference. The capital ratio is the percentage of a bank's capital