The value of the shares goes up because, even if the business and profitability stays exactly the same, with fewer out standing shares, the earnings per share goes up.
The market responds to announcements of buybacks because they offer new information, often called a signal, about a company’s future and hence its share price.
One well-known positive signal in a buyback is that management seems to believe that the stock is undervalued. Executives can enhance this effect by personally purchasing significant numbers of shares, since market participants see them as de facto insiders with privileged information about future earnings and growth prospects. A second positive signal is management’s confidence that the company doesn’t need the cash to cover future commitments such as interest payments and capital expenditures.
But there is a third, negative, signal with a buyback: that the management team sees few investment opportunities ahead, suggesting to investors that they could do better by putting their money elsewhere. Some managers are reluctant to launch buyback programs for this reason, but the capital market’s mostly positive reaction to such announcements indicates that this signal isn’t an issue in most cases. In fact, the strength of the market’s reaction implies that shareholders often realize that a company has more cash than it can invest long before its management does.
Therefore, the overall positive response to a buyback may well result from investors being relieved that managers aren’t going to spend a company’s cash on inadvisable mergers and acquisitions or on projects with a negative net present value. In many cases, a company seems to be undervalued just before it announces a buyback, reflecting an uncertainty among investors about what management will do with excess funds.
Such shareholder skepticism would be well founded. In many industries, management teams have historically allocated cash reserves poorly. The oil industry since 1964 is one example (Exhibit 4): a huge price umbrella for much of this period, courtesy of the Organization of Petroleum Exporting Countries (OPEC), provided oil companies with relatively high margins. Nevertheless, for almost three decades the spread between ROIC and cost of capital for the industry as a whole was negative. Convinced that on a sustained basis the petroleum industry could not deliver a balanced source of income, many companies committed their excess cash to what turned out to be value-destroying acquisitions or other diversification strategies. For example, in the 1970s, Mobil bought retailer Montgomery Ward; Atlantic Richfield purchased Anaconda, a metal and mining company; and Exxon bought a majority stake in Vydec, a company specializing in office automation. All of these cash (or mostly cash) acquisitions resulted in significant losses."
This McKinsey article is old but explores the topic in some detail.
http://www.mckinsey.com/business-functions/strategy-and-corp...
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"Sending signals
The market responds to announcements of buybacks because they offer new information, often called a signal, about a company’s future and hence its share price.
One well-known positive signal in a buyback is that management seems to believe that the stock is undervalued. Executives can enhance this effect by personally purchasing significant numbers of shares, since market participants see them as de facto insiders with privileged information about future earnings and growth prospects. A second positive signal is management’s confidence that the company doesn’t need the cash to cover future commitments such as interest payments and capital expenditures.
But there is a third, negative, signal with a buyback: that the management team sees few investment opportunities ahead, suggesting to investors that they could do better by putting their money elsewhere. Some managers are reluctant to launch buyback programs for this reason, but the capital market’s mostly positive reaction to such announcements indicates that this signal isn’t an issue in most cases. In fact, the strength of the market’s reaction implies that shareholders often realize that a company has more cash than it can invest long before its management does.
Therefore, the overall positive response to a buyback may well result from investors being relieved that managers aren’t going to spend a company’s cash on inadvisable mergers and acquisitions or on projects with a negative net present value. In many cases, a company seems to be undervalued just before it announces a buyback, reflecting an uncertainty among investors about what management will do with excess funds.
Such shareholder skepticism would be well founded. In many industries, management teams have historically allocated cash reserves poorly. The oil industry since 1964 is one example (Exhibit 4): a huge price umbrella for much of this period, courtesy of the Organization of Petroleum Exporting Countries (OPEC), provided oil companies with relatively high margins. Nevertheless, for almost three decades the spread between ROIC and cost of capital for the industry as a whole was negative. Convinced that on a sustained basis the petroleum industry could not deliver a balanced source of income, many companies committed their excess cash to what turned out to be value-destroying acquisitions or other diversification strategies. For example, in the 1970s, Mobil bought retailer Montgomery Ward; Atlantic Richfield purchased Anaconda, a metal and mining company; and Exxon bought a majority stake in Vydec, a company specializing in office automation. All of these cash (or mostly cash) acquisitions resulted in significant losses."