Billionaire Warren Buffett Can't Stop Buying Shares of a Historically Cheap Legal Monopoly, but Also Dumped Nearly a Third of His Stake in Another Monopoly

Though publicly traded legal monopolies are somewhat of a rarity, the Oracle of Omaha oversees two in Berkshire Hathaway's investment portfolio.

The sun is setting on one of Wall Street's most illustrious investing careers. By the end of the year, Berkshire Hathaway ( BRK.A -0.45% ) ( BRK.B -0.46% ) CEO Warren Buffett will retire as his company's day-to-day leader and hand the reins over to Greg Abel.

During the Oracle of Omaha's 60 years at the helm, he's overseen a jaw-dropping cumulative return of 6,061,316% for his company's Class A shares (BRK.A), as of the closing bell on Sept. 5. On an annualized basis, Buffett nearly doubled up the total return, including dividends, of the benchmark S&P 500 .

In addition to a phenomenal investing track record, Berkshire's billi