Determinants of capital adequacy and voluntary capital buffer among microfinance institutions in an emerging market

This study examines the determinants of capital adequacy and voluntary capital buffers among microfinance institutions (MFIs). We apply the two-stage least squares (2SLS) with instrumental variables to account for endogeneity. Using quarterly panel data of 439 MFIs in Ghana covering the period 2015–2018, the study found that credit risk, income diversification, size, profitability, lending channel, and equity-to-asset ratio significantly affect capital adequacy. Also, the factors that drive voluntary capital buffers are income diversification, size and equity-to-asset ratio, but size and economic growth are insignificant when the upper limits of Basel III requirements are applied. Generally, the results are insignificant among non-deposit-taking (i.e. Tier 3 like Financial NGOs) MFIs. The findings show that non-performing loans negatively affect capital adequacy. Income diversification increases capital adequacy, especially among deposit-taking MFIs which have the regulatory liberty to engage in additional financial intermediation activities. Size has an inverted U-shape nexus with capital adequacy and there is evidence to suggest that for non-deposit-taking MFIs, size may not matter. Profitability increases capital adequacy while equity-to-asset ratio decreases capital adequacy, especially among deposit-taking MFIs. Additionally, lending channels negatively affect capital adequacy, especially among deposit-taking MFIs. Economic growth reduces capital adequacy but results are insignificant when we control for quarter fixed-effects. These results throw light on the application of the capital buffer theory in the context of MFIs which provides useful insights for practitioners, regulators, policymakers and academia.

本研究聚焦于小额信贷机构（microfinance institutions, MFIs）的资本充足率（capital adequacy）与自愿资本缓冲（voluntary capital buffers）的决定因素。我们采用工具变量（instrumental variables）结合两阶段最小二乘法（two-stage least squares, 2SLS）的方法，以控制内生性（endogeneity）问题。基于加纳439家小额信贷机构2015至2018年的季度面板数据（quarterly panel data），本研究发现信用风险（credit risk）、收入多元化（income diversification）、机构规模、盈利能力、放贷渠道以及股权资产比（equity-to-asset ratio）对资本充足率存在显著影响。
此外，驱动自愿资本缓冲的因素包括收入多元化、机构规模与股权资产比，但当采用巴塞尔协议III（Basel III）监管要求的上限标准时，机构规模与经济增长的影响并不显著。整体而言，不吸收存款类（即三级小额信贷机构，如金融非政府组织）的小额信贷机构的相关实证结果均不显著。
研究结果显示，不良贷款（non-performing loans）对资本充足率具有负向作用。收入多元化能够提升资本充足率，这一效应在具备开展额外金融中介活动监管自主权的吸收存款类小额信贷机构中尤为明显。机构规模与资本充足率呈倒U型关联，且有证据表明，对于不吸收存款的小额信贷机构而言，机构规模并非关键影响因素。盈利能力可提升资本充足率，而股权资产比则会降低资本充足率，该现象在吸收存款类小额信贷机构中更为突出。此外，放贷渠道对资本充足率具有负向影响，这一效应在吸收存款类小额信贷机构中尤为显著。经济增长会降低资本充足率，但在控制季度固定效应（fixed-effects）后，该结果不再显著。
上述研究结果阐明了资本缓冲理论（capital buffer theory）在小额信贷机构场景中的应用，为行业从业者、监管机构、政策制定者及学术界提供了极具参考价值的见解。