Codetermination did not lower German profits.
Overall productivity and profitability declined for German codetermined firms that went from 1/3 to 1/2 parity from 1975 - 1983.
Following Germany's 1976 strengthening of codetermination laws to 1/2 board representation for 2,000+ employee firms, capital-labor ratios declined (favoring capital formation), productivity declined, and profitability increased.
Codetermination and Enterprise Performance: Empirical Evidence from West Germany
Economic Effects of Codetermination
Labor In the Boardroom
Michael A. Gurdon