Due to the government-driven mergers of large banks, many competing firms in Japan ended up borrowing from a common lender. Using firm-level data, we find that the capital investments of competing firms that share a common lender decrease by 15% of the mean. When a common lender can exercise its voice through its former employees serving as firms’ executive directors, investments fall significantly further. Competing firms that share a common lender increase markups and profitability ratios, suggesting that the lender induces strategic coordination among its borrowers to reduce their competitive pressures. Firms use saved resources from weaker competition for cash cushions.

We show that political polarization among directors negatively affects corporate board effectiveness by reducing forced CEO turnover-performance sensitivity. Our results are more pronounced in presidential election years and for firms with more monitoring and advising needs. Polarization also increases the departure likelihood for directors who are ideologically distant from the rest of the board, making boards more politically homogeneous over time. Finally, we show that polarization in the boardroom lowers firms' investment- Q sensitivity and Environmental, Social and Governance (ESG) performance. Our findings highlight the real economic cost of political polarization.