OMAHA, Neb. (AP) - Investor Warren Buffett says last year was "subpar" for his company even after posting a 45 percent increase in profit, because the value of Berkshire Hathaway (BRK-A, BRK-B) trailed the overall market.

Buffett said Friday that 2012 was only the ninth time in the past 48 years that Berkshire's book value per share failed to outpace the S&P 500.

The legendary investor also confessed that the two investment managers he hired over the last few years left Buffett in their dust.

Berkshire's net income soared in 2012 to $14.8 billion, up from $10.3 billion the previous year, but most of the increase came from paper gains on its investments and derivative contracts.

Without the paper gains, Berkshire's operating earnings advanced 17 percent to $12.6 billion, up from the previous year's $10.8 billion.