“The bear market is officially over,” Bank of America’s top strategist Savita Subramanian declared in a Friday message to clients.

Subramanian noted the S&P has returned 19% on average in the 12 months immediately following a 20% rally from a bottom; this would send the S&P to an all-time high of about 5,100.

There's more upside left in stocks after a new bull market started on Thursday, according to Bank of America.

"After crossing the +20% mark from the bottom, the S&P 500 continued to rise over the next 12 months 92% of the time," BofA said.

Additionally, stocks do well after the 20% bull market threshold is reached, based on historical data. That's based on data since the 1950s and is compared to a 12-month winning ratio of just 75% and an average overall 12-month return of 9%.

"We don't put a lot of stock (pun intended) in arbitrary definitions, but note that after crossing the +20% mark from the bottom, the S&P 500 continued to rise over the next 12 months 92% of the time, returning 19% on average," Subramanian said.

The S&P inched up 0.1% to just shy of 4,300 Friday, set to close at its highest price since last April; the index is now up 23% since it bottomed out at 3,491 in October, when the S&P crashed nearly 30% in a span of 10 months.

The S&P 500 rose to its highest level in more than a year Friday, sending stocks into a technical bull market but leading to a split among experts about whether the rally will keep on chugging or falter as it grapples with concerns that prices are running too hot.