Margins and price limits in Taiwan's stock index futures market

This study extends the framework of Brennan (1986) to find the cost-minimizing combination of spot limits, futures limits, and margins for stock and index futures in the Taiwan market. Our empirical results show that the cost-minimization combination of margins, spot price limits, and futures price limits is 7 percent, 6 percent, and 6 percent, respectively, when the index level is less than 7,000. When the index level ranges from 7, 000 to 9, 000, the efficient futures contract calls for a combination of 6 5 percent, 5 percent, and 6 percent. The optimal margin, reneging probability, and corresponding contract cost are less than those without price limits. Price limits may partially substitute for margin requirements in ensuring contract performance, with a default risk lower than the 0.3 percent rate that is accepted by the Taiwan Futures Exchange. On the other hand, though imposing equal price limits of 7 percent on both the spot and futures markets does not coincide with the efficient contract design, it does have a lower contract cost and margin requirement (7.75 percent) than that without imposing price limits (8.25 percent).