Though policy rates have not been raised for more than a year, the Central Bank said market interest rates have been allowed to go up.
"Accordingly, market interest rates adjusted upwards and continued to remain at a higher level," the Central Bank said.
"This has led to a substantial decline in the demand for money, helping to maintain reserve money well below the targeted level during the first quarter of 2008."
Reserve money is a narrow measure of money which measures the reserves of the banking sector which forms a base to drive money supply in the country.
The monetary authority targets reserves in the hope of influencing credit and a broader supply of money and ultimately inflation.