The art of unethical investing

Ethical investing -- where you avoid investing in businesses that engage in activities that you disapprove of -- was first practiced by the Quakers in 1758 when they disinvested from the slave trade. It took off in the 1970s, spurred on by the anti-apartheid movement, and most large fund management groups nowadays offer ethical investment funds.

The problem is that the definition of "ethical" is highly subjective -- and companies that some investors say are "unethical", such as those operating in the alcohol, defence and oil industries, often beat the market.