Arbitrage
Arbitrage is the simultaneous purchase and sale of an asset in different markets or forms to profit from a price discrepancy, theoretically providing a risk-free return that also helps bring prices in the two markets into alignment.
Pure arbitrage — the exploitation of identical price discrepancies without residual risk — was largely theoretical in perfectly efficient markets. In practice, what practitioners described as arbitrage encompassed a spectrum of strategies ranging from near-riskless cash-futures arbitrage to the far riskier 'risk arbitrage' or 'merger arbitrage' that involved event-driven uncertainty. The common thread was capitalising on pricing relationships that were temporarily out of alignment, with the expectation that convergence would occur within a known or probable timeframe.
In Indian equity markets, cash-futures arbitrage was among the most widely practised institutional strategies. When NSE Nifty futures traded at a premium to the spot index value that exceeded the risk-free rate adjusted for dividends and time, arbitrageurs purchased the cash basket of stocks and simultaneously sold the futures contract, locking in the spread to be earned as the basis converged toward expiry. This strategy was the foundation of many arbitrage mutual funds in India — a fund category that attracted significant inflows from conservative investors seeking equity-like tax treatment with fixed-income-like volatility.
ETF arbitrage was another active domain. When an ETF's market price deviated from the Net Asset Value (NAV) of its underlying basket — a deviation that could occur due to supply-demand imbalances in the ETF's units — authorised participants (APs) could create or redeem ETF units by delivering the underlying basket to the fund or receiving it back, profiting from the spread and simultaneously pushing the ETF price back toward NAV. This mechanism kept Indian ETF prices closely tethered to their underlying benchmarks and was conducted by institutional participants with the operational infrastructure to handle physical basket creation and redemption.
SEBI's cross-exchange arbitrage between NSE and BSE for cash equity became progressively less common as the electronic unification of Indian markets made price differences between the two exchanges vanishingly small and fleeting. However, opportunities persisted in less liquid securities, particularly in the SME segment, and in situations involving corporate actions where the adjustment of prices across instruments or exchanges created temporary dislocations.
Statistical arbitrage — pairs trading or multi-leg strategies that exploited historical price correlations — occupied the boundary between pure arbitrage and directional speculation. These strategies required sophisticated quantitative models to identify cointegrated pairs and manage reversion risk, and they represented a significant portion of the proprietary trading activity at Indian brokerage desks and domestic hedge funds. Unlike classical arbitrage, statistical arb carried model risk: if the assumed relationship between instruments broke down, losses rather than riskless profits resulted.