Berkshire Hathaways (BRK-A, BRK-B) famed stock portfolio, which typically embodies Warren Buffetts buy and hold maxim, posted stellar returns in 2019.

Some of the top holdings include American Express (AXP), Apple (AAPL), Bank of America (BAC), and Delta Airlines (DAL), according to Buffetts widely-read annual letter.

Buffett wrote that he doesn't view these investments as "stock market wagers dalliances to be terminated because of downgrades by 'the Street,' an earnings' miss,' expected Federal Reserve actions, possible political developments, forecasts by economists or whatever else might be the subject du jour."

Rather than stock holdings, Buffett views these as companies Berkshire Hathaway "partly owns." He added that these are companies "earning more than 20% on the net tangible equity capital required to run their businesses" and are profitable "without employing excessive levels of debt

1. Using your best financial accounting skills honed in class, try to explain the common factors that have led Warren Buffet to have such great success in seeing the value of his stocks increase over time.

2. Some companies like Coca Cola and American Express have increased massively on a percentage basis. Why so much for these stocks?

3. A quick but discerning look at Berkshire Hathaways stock documents will reveal uncommonly high ROI for the portfolio over time. Why?

4. Are there any real manufacturing companies in the list? Why or why not?

5. Other companies owned by Berkshire such as Geico, Dairy Queen and Sees candies are not on the list. Why the special treatment?