A share buyback, also known as a stock repurchase, can significantly impact a company's stock price in various ways. Primarily, a buyback reduces the number of outstanding shares in the market. With fewer shares available, the earnings per share (EPS) typically increase, assuming net income remains constant. This enhanced EPS can make the stock more attractive to investors, often leading to a rise in the stock price.

Furthermore, buybacks can signal management’s confidence in the company’s future prospects. When a company repurchases its own shares, it indicates that management believes the stock is undervalued and that investing in its own shares is the best use of capital. This positive signal can boost investor sentiment, driving up the stock price.

Additionally, share buybacks can improve financial ratios such as return on equity (ROE) and return on assets (ROA), making the company appear more financially healthy and efficient. These improved metrics can attract more investors, further increasing the stock price.

However, the impact on the stock price can also depend on the overall market conditions and investor perception. If the buyback is seen as a means to artificially inflate the stock price without improving the underlying business fundamentals, it may lead to skepticism and could potentially have a limited or even negative effect on the stock price. Therefore, while buybacks often result in a positive stock price reaction, the context and execution are crucial.