controlling for country‐specific fixed effects and nonlinear effects caused by network externalities. Albiman and Sulong (2016) showed that mobile phone and internet were main economic growth drivers in the long run using data in 45 Sub‐Saharan African countries from 1990 to 2014.

Infrastructure can contribute to productivity and economic growth through several channels:

- Infrastructure can lower production costs. Seethepalli et al. (2008) found that telecommunications, electricity, roads, water, and sanitation have significant positive impact on economic growth in East Asia, after controlling human capital and total investment. Similarly, Straub and Terada‐Hagiwara’s study (2010) showed the growth rate of these infrastructure stocks promotes economic growth in most countries in East Asia and South Asia. For production, electricity is often a major constraint in developing countries. Dollar et al. (2005) showed that the inconsistent power supply has strong negative impacts on productivity using firm level survey data. Firms often have to rely on their own generators to supplement the unreliable public electricity supply. However, the cost of maintaining a power generator is often high and burdensome, especially for small and medium firms, where a large share of the poor and vulnerable are employed. Hallaert et al. (2011) found electricity supply is a major constraint to trade expansion in developing countries.

- Infrastructure can lower transactions costs. Limao and Venables (2001) showed poor infrastructure accounts for more than 40 percent of transport costs. Radelet and Sachs (1998) found that a doubling of the shipping cost is associated with slower annual growth of slightly more than half of one percentage point. Cordella and Simon (1997) found that infrastructure can reduce transaction costs (including the costs for gathering information, evaluating alternative options, negotiating, and contracting) by reducing time and cost in communication and information exchange and by flattening the organizational structure to reduce information flux and coordination needs.  Lakshmanan (2011) suggested that time and cost savings due to transport infrastructure improvement can better link product and factor markets, promote inter‐regional trade and specialization, increase returns to scale, and reallocate economic activities.

- Infrastructure can increase total factor productivity. Good infrastructure can increase efficiency of conventional inputs (Duggal et al., 1999). Interconnections and complementarities between infrastructures help improve service efficiency and support innovative technologies adoption (Bottini et al., 2012). Based on a large‐scale firm‐level survey data from China, Wan and Zhang (2017) explored the causality between infrastructure and firm total factor productivity, and concluded that roads, telecommunication servers, and cable promote firm productivity. In addition to the conventional productivity effect, Fay et al. (2011) found that infrastructure is likely to condition the efficiency of many key areas of productive factors, such as the costs of investment adjustment, the durability of private capital, and both demand for and supply of health and education services. Dam (2007) showed that the rule of law is important to unlocking the developing world's full growth potential.

- Infrastructure services can “crowd in” other productive inputs. Calderón and Servén (2014) suggested an increase in infrastructure stock or improvement in infrastructure

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