Fossil Fuel Beta (FFß) measures the percent change in excess (market-adjusted) stock returns for every 1 percent increase in fossil fuel prices. For example, if a company (or industry) has an FFß of –0.20, then a 1 percent increase in fossil fuel prices should produce, on average, a 0.2% decline in the firm's stock price over and above the impact arising from fossil fuel price swing on the stock market as a whole. (Conversely, a 1 percent decrease in fossil fuel prices should produce, on average, an equivalent increase in stock price.)