Network Shapley-Shubik Power Index: Measuring Indirect Influence in Shareholding Networks

Extending the Shapley-Shubik power index to networks, we propose a new measure and numerical method to calculate the indirect influence of investors on companies: Network power index (NPI). While the original index, reflecting the characteristics of majority vote in a shareholders meeting, measures the direct voting power of a shareholder, NPI captures not only an investor’s direct influence over a company but also indirect influence over this company’s subsidiary. Since NPI is often incalculable in a large network, we present a new method to numerically compute NPI: label propagation. Applying this method to the global shareholding networks in 2016, we find NPIs and raw vote shares dramatically diverge for some investors and this discrepancy suggests the difference in investment strategies between governments and private financial institutions.