Svanberg owns 925,000 BP shares. A month after he took over as chairman of the oil giant in January, he purchased 750,000 shares in the company at 5.75 pounds ($8.87), newspaper Dagens Industri reported on Thursday.
Their value increased to 6.55 pounds per share by the time the offshore oil drilling rig Deepwater Horizon exploded off the coast of Louisiana in the Gulf of Mexico on April 20th.
Only a week after the accident, Svanberg bought an additional 175,000 shares at 6.19 pounds, unaware of the impending implications of the disaster. Only later, according to Dagens Industri, did the accident's enormous economic implications become clear to BP and its share values collapsed over the summer.
On Wednesday, according to the share price in pounds, Svanberg's holdings had declined in value to about 40 million, compared with the 62 million he paid for the shares. On the New York Stock Exchange, shares have traded in a 52-week range of $26.75 to $62.38.
Svanberg is one of Sweden's largest private shareholders, with major holdings in Ericsson, Melker Schörling and Assa Abloy, the report added. On Wednesday afternoon, the value of his holdings were 797 million kronor.