The BSE share price is falling today primarily due to a combination of factors including concerns over high US tariffs imposed on Indian exports, regulatory challenges affecting trading volumes on the exchange, and a general weak investor sentiment influenced by global market uncertainties. Key reasons for the fall today include:

• The imposition of 50% tariffs by the US on Indian goods has created uncertainty and pressure on exporters, negatively impacting market sentiment. This trade tension is a major factor dragging down the BSE and other Indian indices today.

• Regulatory actions by SEBI considering changes to weekly expiry contracts, which could reduce trading volumes and thereby impact BSE's transaction fee revenue, have caused investor apprehension about BSE’s near-term earnings.

• Persistent selling by Foreign Institutional Investors (FIIs) amid weak global conditions and disappointing cues from Asian and US markets are also contributing to the decline.

• Technical signs of weakness and the broad market selloff driven by these factors result in BSE shares falling about 3.77% today, with prices dropping over Rs 80 from yesterday's close.

In summary, the fall in BSE shares today is mainly due to the impact of US tariffs on India, regulatory uncertainties regarding trading contract tenures, ongoing foreign investment outflows, and overall cautious market sentiment amid global uncertainties.