The BSE share price is falling primarily due to multiple factors including concerns over US tariffs impacting trade with India, regulatory uncertainties, and profit-taking after high valuations. Specifically:

• The Trump administration's plan to impose potentially high tariffs (up to 50%) on Indian exports has created uncertainty and negative sentiment about India's trade outlook, contributing significantly to stock market declines including BSE shares.
• Regulatory concerns emerged after the Securities and Exchange Board of India (SEBI) indicated a possible extension of equity derivatives contract tenures, which could reduce BSE's lucrative weekly-expiry volumes, affecting its profitability and investor confidence.
• Foreign Institutional Investors (FIIs) have been consistently selling Indian equities, including BSE shares, reducing market support.
• Global market volatility, including declines in Asian peers and uncertainty in US monetary policy, has also weighed on investor sentiment.
• Additionally, some profit booking occurred after recent gains, especially in financial and IT sectors, which include BSE linked stocks.
• Specific internal developments like the resignation of BSE's Chief Information Officer for health reasons have also had minor negative impacts on the stock.

Overall, these combined global and domestic factors have resulted in a sharp fall in BSE share price, with recent drops over 3-6% following these developments and fears of prolonged market volatility.