How effective have antitrust laws been in breaking up existing monopolies?

What will be an ideal response?

It is difficult to judge the effectiveness of antitrust laws. The government generally has been lenient in applying antitrust laws to large firms that have grown “naturally” in the expansion of their market shares. Antitrust laws have not been applied in most cases unless a firm has more than 60% of the relevant market and there is evidence the firm used abusive conduct to achieve or maintain its market dominance. Two noteworthy examples of the use of antitrust laws to alter market structure in an industry are the 1982 AT&T case and the 2000 Microsoft case. In 1982, there was a settlement out of court by the government and AT&T (the telephone company). It was charged with violating the Sherman Act by engaging in several anti competitive actions to keep its domestic monopoly in telephone communications. AT&T agreed to divest itself of its 22 regional phone-operating companies. In 2000, a Federal district court ruled that Microsoft violated the Sherman Act by using anti-competitive tactics to maintain and expand its software dominance. The ruling from the court called for the division of Microsoft into two firms, but the ruling was overturned. Instead, Microsoft was prohibited from engaging in anti competitive business practices.