Hi, Gurpal
It is true that the EUR/USD is the most heavily-traded currency pair.
And, it is also true that the GBP/USD exhibits greater price volatility than the EUR/USD.
However, these two facts are not related to one another: there is no correlation (positive or negative) between total worldwide trading volume, and average daily price volatility.
Let’s look at these two facts, one at a time.
1. Regarding trading volume: According to the Bank for International Settlements (BIS), the EUR/USD accounts for 27% of all foreign exchange transactions worldwide. The GBP/USD accounts for 12%.
There are many reasons for the dominance of the EUR/USD in worldwide foreign exchange. The primary reasons are: the U.S. and the Euro Zone represent the two largest economies in the world; the USD is the established reserve currency of the world; and the EUR is widely held around the world as a “second” reserve currency.
2. Regarding price volatility: The most common measure of price volatility is the average true range (ATR). Below are two charts showing the Daily ATR(14) over the past 2 years for the GBP/USD and the EUR/USD. Notice that the ATR for each currency pair peaked on November 5, 2008, and then declined significantly to the present time.
We can compare the price volatility of these two pairs with a simple ratio.
On November 5, 2008, when volatility was exceptionally high, the Daily ATR(14) of the GBP/USD (550 pips) was 57% greater than the ATR(14) of the EUR/USD (350 pips).
Today, January 4, 2010, when volatility in both pairs is low, the ratio is lower: nevertheless, the Daily ATR(14) of the GBP/USD (158 pips) is still 33% greater than the ATR(14) of the EUR/USD (119 pips).
It’s difficult to find a convincing explanation for why the GBP/USD is so volatile — and why the GBP/JPY is even more volatile.
One theory suggests that high volatility attracts speculators, and increased speculation causes increased volatility. Thus, a positive feed-back loop is set up, which tends to perpetuate itself. There are probably other, equally plausible, theories.
I hope this answers your questions.
Clint