The KRX calculates the margin based on the net risk exposure of the total portfolios of the futures and options held. The margin per product group of underlying assets with similar characteristics – stock indices, stocks, bonds, currencies, commodities and etc. - is calculated first and the margins of individual groups are simply added up to calculate the margin. The margin rates applied in margin calculations are, in principle, determined to reflect the price volatility of the underlying assets as well as the characteristics of each derivatives product and the market situation. In order to help investors understand the margining system, the KRX circulates PC COMS, a free PC-based education program.