Anyone researching Bank Of Ireland Group plc (ISE:BIRG) might want to consider the historical volatility of the share price. Volatility is considered to be a measure of risk in modern finance theory. Investors may think of volatility as falling into two main categories. First, we have company specific volatility, which is the price gyrations of an individual stock. Holding at least 8 stocks can reduce this kind of risk across a portfolio. The other type, which cannot be diversified away, is the volatility of the entire market. Every stock in the market is exposed to this volatility, which is linked to the fact that stocks prices are correlated in an efficient market.
Some stocks see their prices move in concert with the market. Others tend towards stronger, gentler or unrelated price movements. Beta is a widely used metric to measure a stock's exposure to market risk (volatility). Before we go on, it's worth noting that Warren Buffett pointed out in his 2014 letter to shareholders that 'volatility is far from synonymous with risk.' Having said that, beta can still be rather useful. The first thing to understand about beta is that the beta of the overall market is one. Any stock with a beta of greater than one is considered more volatile than the market, while those with a beta below one are either less volatile or poorly correlated with the market.
See our latest analysis for Bank Of Ireland Group
What BIRG's beta value tells investors
Zooming in on Bank Of Ireland Group, we see it has a five year beta of 1.52. This is above 1, so historically its share price has been influenced by the broader volatility of the stock market. If this beta value holds true in the future, Bank Of Ireland Group shares are likely to rise more than the market when the market is going up, but fall faster when the market is going down. Many would argue that beta is useful in position sizing, but fundamental metrics such as revenue and earnings are more important overall. You can see Bank Of Ireland Group's revenue and earnings in the image below.
How does BIRG's size impact its beta?
Bank Of Ireland Group is a fairly large company. It has a market capitalisation of €4.0b, which means it is probably on the radar of most investors. It takes a lot of money to influence the share price of large companies like this one. That makes it interesting to note that its share price has a history of sensitivity to market volatility. There might be some aspect of the business that means profits are leveraged to the economic cycle.