Base on article summary below, identify an important public finance principle that is used in this case, explain how it is used, evaluate its use as being efficient or inefficient, and recommend an efficiency improvement, if inefficient.

The article under the impact of financial development on economic growth in SubSaharan Africa, which is subdivided into low, middle and upperincome groupings to ascertain whether differences in income levels across countries affect the relative impact of finance on growth . Based on the research and findings, The financial depth and financial intermediation reduce per capita income growth in low and middleincome countries. However, it increases growth in upperincome and the overall sample of SSA countries. Credit supply positively impacts growth in lowincome countries but exerts a significantly negative impact on growth in middleincome and the overall sample of SSA countries. Financial liberalization promotes growth in upperincome and the overall SSA . In addition, financial development is considered as both supply-leading and demand-following. The supply-leading hypothesis argues that financial institutions and markets increase the supply of financial services, thereby inducing real economic growth. Meanwhile, the demand following hypothesis posits that economic growth increases the demand for financial services, thus inducing an expansion in the financial sector as the real economy grows . However, the growing concern for most African countries in progressing on the weak development of the 1970s, the development of the financial system has picked up significant momentum from policymakers over the locale, with specific center on supporting money related improvement. Most African nations have tested with policies of money related sector changes that are mostly propelled by the basic adjustment programs promoted by the World Bank and the International Monetary Fund (IMF).