Given almost biblical gloom about the world economy at the moment, you really have to do a double take looking at Wall Street’s so-called “Fear Index”. The ViX , which is essentially the cost of options on S&P500 equities, acts as a geiger counter for both U.S. and global financial markets. Measuring implied volatility in the market, the index surges when the demand for options protection against sharp moves in stock prices is high and falls back when investors are sufficiently comfortable with prevailing trends to feel little need to hedge portfolios. In practice — at least over the past 10 years — high volatility typically means sharp market falls and so the ViX goes up when the market is falling and vice versa. And because it’s used in risk models the world over as a proxy for global financial risk, a rising ViX tends to shoo investors away from risky assets while a falling ViX pulls them in — feeding the metronomic risk on/risk off behaviour in world markets and, arguably, exaggerating dangerously pro-cyclical trading and investment strategies.