Socially Responsible Divestment

Blanket exclusion of "brown" stocks is seen as the best way to reduce their negative externalities by starving them of capital. We show that a more effective strategy may be tilting -- holding a brown stock if the firm has taken a corrective action. While such holdings allow the firm to expand, they also encourage the action. We derive conditions under which tilting dominates exclusion for externality reduction. If the action is not publicly observable, the investor might not tilt even if she can gather private information on the action -- tilting would lead to accusations of greenwashing. The presence of an arbitrageur who buys underpriced stocks increases the relative effectiveness of tilting. A responsible investor who is partially profit-motivated may be more likely to tilt than one whose sole objective is minimizing externalities.