OMAHA, Neb. (AP) — Billionaire Warren Buffett's company added to its already substantial Apple investment at the end of last year while slashing a new investment in computer chip maker Taiwan Semiconductor and two longtime bank holdings.

Berkshire Hathaway Inc. revealed several changes to its stock portfolio in documents filed with the Securities and Exchange Commission Tuesday. Many investors follow the company's moves closely because of Buffett's remarkably successful investing record over the decades.

Berkshire picked up nearly 21 million more shares in the iPhone maker during the final three months of last year to give it 915.6 million shares at the end of 2022.

Buffett has called Apple one of the four giants that drive Berkshire's results even though it is only a stock investment. Berkshire's other main drivers are companies that it owns outright: its insurance unit that includes Geico, its energy company that owns several major utilities, and BNSF railroad.

During the quarter, Berkshire slashed its investments in Taiwan Semiconductor, US Bancorp and Bank of New York Mellon.

Just three months after revealing a 60 million-share stake in the chipmaker, Berkshire cut its Taiwan Semiconductor investment down to 8.3 million shares.

Berkshire also cut its US Bancorp investment drastically from 52.5 million shares to 6.7 million by the end of the year.

Berkshire Hathaway cut its investment in Bank of New York Mellon again and sold off more than 37 million shares during the quarter to leave it with just over 25 million shares of the bank.

The quarterly filings Berkshire submitted Tuesday don't make clear which investments Buffett is responsible for and which ones were made by the company's two other investment managers, but Buffett generally handles all of Berkshire's biggest investments worth $1 billion or more. Buffett doesn't regularly comment on these stock filings.

Berkshire also added to one of its smaller investments that it first revealed three months ago when it picked up more than 1.2 million Louisiana Pacific shares to give it control of nearly 10% of that maker of building products.

During the quarter, Buffett continued to trim Berkshire's investment in Activision Blizzard to 52.7 million shares. He has said that he bought that stock as a way to bet that Microsoft's acquisition of the video game maker will ultimately go through.

The Omaha, Nebraska-based conglomerate Buffett leads also trimmed its investments in the grocer Kroger and Ally Financial.

Buffett's biggest investment over the past year in oil producer Occidental Petroleum remained unchanged during the quarter. Berkshire held 194.4 million Occidental shares and warrants to buy another 83.9 million shares at the end of the year.

Berkshire did pick up nearly 2 million more Chevron shares during the quarter to give it control of 8.7% of the oil giant.

One of the biggest changes in Berkshire's portfolio isn't reflected in the SEC filings because its investment in Chinese electric car maker BYD is held on the Hong Kong stock exchange. Since August, Berkshire has sold off 95 million of the 225 million BYD shares it bought back in 2008.

Besides stocks, Berkshire owns an eclectic mix of dozens of different manufacturing, retail and service businesses.