Why one heavyweight can move the entire index

is an important lesson in index concentration risk. On 27 August, HDFC Bank fell 2.2% and touched its lowest level in nearly 2½ years. Investor concerns include a reported U.S. class-action lawsuit involving alleged payments to Maharashtra State Road Development Corporation and uncertainty over CEO Sashidhar Jagdishan's renewal, with his current term ending in October. Reuters reported that the stock has fallen more than 25% in 2026. Learning for beginners: Never assume that a large, well-known company is automatically a low-risk investment. Investors must monitor corporate governance, regulatory developments, management continuity, asset quality and valuation along with earnings. Because HDFC Bank has a substantial index weight, weakness in the stock can also influence Nifty performance.