ON Tuesday, the rupee fell so fast against the dollar that a gap opened between the inter-bank and open-market rates sufficient to allow hundi operators to get back into the business they had abandoned about a decade ago, when the State Bank first acted to unify rates. The spread of Rs 1.20 between the two rates is more than enough for hundi traders to get back into business. This adds to the worries of the State Bank as it tries, rather vainly, to defend the rupee against all the pressures it is facing. It will have to try and shut down the illegal business. That can only be done when the rupee's inter-bank value is roughly the same as in the open market. Otherwise the hundi business will rear its head against virtually all that the State Bank can throw at it. So far, the State Bank has tried a jacking up of interest rates, as well as an overhaul revision of its regulations governing the inter-bank markets, but it has had virtually no effect against the double-whammy that has hit foreign exchange markets, not just in Pakistan, but the world over: oil and food. As the main regulator of foreign exchange, the State Bank must take appropriate corrective measures to stop the slide.