What is the difference between the A shares and B shares of Berkshire? Why do the B shares sometimes sell for a discount to the A shares?

"Berkshire Hathaway Inc. has two classes of common stock designated Class A and Class B. A share of Class B common stock has the rights of 1/30th of a share of Class A common stock with these exceptions: First, a Class B share has 1/200th of the voting rights of a Class A share (rather than 1/30th of the vote). Second, the Class B shares are not eligible to participate in the Berkshire Hathaway Inc. shareholder designated contributions program. Press HERE for a description of the program. Additionally, each share of a Class A common stock is convertible at any time, at the holders option, into 30 shares of Class B common stock. This conversion privilege does not extend in the opposite direction. That is, holders of Class B shares are not able to convert them into Class A shares. Both Class A & B shareholders are entitled to attend the Berkshire Hathaway Annual Meeting which is held the first Monday in May." In my opinion, most of the time, the demand for the B will be such that it ...