Arbitrage and the Law of One Price in the market for American depository receipts

Ours is the first paper to highlight pairs trading as the main price-correcting mechanism by which arbitrage can maintain stock–ADR parity. We show that arbitraging stock–ADR pairs extracts small per-trade profits which accumulate to a substantial aggregate return. The observed strong tendency of pricing disequilibria to mean-revert, along with the two-way convertibility between stocks and ADRs, mean that arbitrageurs face minimal risks toward price divergence. They do, however, face uncertainty about the duration of individual trades. The magnitude of this uncertainty relates directly to the profit target arbitrageurs set after a long/short position is established. This fact can explain why some disequilibria go unexploited. Overall, our work provides evidence against automatically efficient prices, and supports the view that mispricings incentivize arbitrageurs to enforce market efficiency.     

Optimal foreign debt for Egypt: A stochastic control approach

This study assesses the foreign debt policy in Egypt and contrasts it versus the optimal policy during the period 1985–2008. It also presents a forecast of the optimal debt during the period 2009–2014. The optimal debt policy was derived using an open economy model for Egypt. The uncertainties in the model stem from the uncertainties in the interest or debt service payments and the uncertainties in the rate of return on investments. The stochastic control approach was used to find the optimal debt policy. It was found that Egypt could borrow externally as long as the trend in the rate of return on investments exceeds the trend in the real interest rate or the trend in the rate of the debt service payments. The analysis finds that Egypt's foreign debt was higher than the optimal level before 1997. After 1997, foreign debt seems to converge to the optimal level. However, Egypt's foreign debt is still below its optimal level which results in an opportunity cost for the economy to grow, otherwise, GDP could have recorded a favorable increase.     

A Market Efficiency Comparison of Islamic and Non-Islamic Stock Indices

This article examines the martingale difference hypothesis (MDH) and the random walk hypothesis (RWH) for nine conventional and nine Islamic stock indices: Asia-Pacific, Canadian, Developed Country, Emerging, European, Global, Japanese, UK, and United States. It investigates whether Islamic stock indices are more, less, or as efficient as their conventional counterparts. We test four sub-periods of bullish and bearish stock markets, together with the financial meltdown and its recovery, over the period 1997–2012. We use the Escanciano and Lobato’s (2009) automatic portmanteau test (AQ) and Deo’s (2000) test for the MDH. We also apply the automatic variance ratio test (AVR) developed by Choi (1999) and Kim (2009) for the RWH. Over the period from 1997 to 2012, we find that three conventional indices (Europe, Japan, and UK) are efficient, but that none of the Islamic indices are efficient in these markets. During the recent financial crisis, our results indicate slightly more efficiency for the Islamic indices than their conventional counterparts. Our study finds that overall the conventional indices are more efficient than their Islamic counterparts. Nevertheless, during periods of general downturns the Islamic indices have shown the same level of efficiency as their counterparts. Furthermore, it appears that during the last two sub-periods under study, the Islamic indices have moved toward efficiency, displaying the same level of efficiency as their counterparts.     

Optimal portfolio selection in nonlinear arbitrage spreads

This paper analytically solves the portfolio optimization problem of an investor faced with a risky arbitrage opportunity (e.g. relative mispricing in equity pairs). Unlike the extant literature, which typically models mispricings through the Ornstein–Uhlenbeck (OU) process, we introduce a nonlinear generalization of OU which jointly captures several important risk factors inherent in arbitrage trading. While these factors are absent from the standard OU, we show that considering them yields several new insights into the behavior of rational arbitrageurs: Firstly, arbitrageurs recognizing these risk factors exhibit a diminishing propensity to exploit large mispricings. Secondly, optimal investment behavior in light of these risk factors precipitates the gradual unwinding of losing trades far sooner than is entailed in existing approaches including OU. Finally, an empirical application to daily FTSE100 pairs data shows that incorporating these risks renders our model's risk-management capabilities superior to both OU and a simple threshold strategy popular in the literature. These observations are useful in understanding the role of arbitrageurs in enforcing price efficiency.