Shares of internet giant Alphabet closed out the day at an all-time high on Monday as big tech companies saw gains that defied the rest of the market.
Google-parent Alphabet closed up 2.7% at $1,397.81 per share, which brings the company's market cap to $964 billion.
Facebook rose almost 1.9% on the day, closing at $212.60 per share, which makes the social media giant worth $606.3 billion -- a 52-week high, and just 3% off its all-time high of $218.62, set on July 25, 2018.
The record highs come as both companies face ongoing antitrust investigations by coalitions of state attorneys general.
In September, 50 attorneys general announced the launch of an investigation into Google over possible antitrust violations in its advertising business. The next month, CNBC reported that the attorneys general were preparing to expand their investigation into Google's Android and search businesses.
Around the same time as the launch of the Google probe, 47 attorneys general announced an antitrust investigation into Facebook's practices, which sent the stock down almost 4% that day.
However, Monday's record highs suggest investors are unconcerned going into the new year about the ongoing investigations.
Alphabet's record high comes nearly a month after former CEO and Google co-founder Larry Page relinquished his role to Sundar Pichai, former Google CEO. Pichai will help the company find new revenue streams, Pivotal Research Group analyst Michael Levine said as he upgraded the stock to a buy rating.
Levine said that regulatory concerns have historically been his firm's biggest concern with Google, but that as the company diversifies revenue into other areas, regulation is a lesser investment risk.
"We are not minimizing the regulatory risk, but Doubleclick/ad-tech stack revenues are predominantly related to GOOG networks," he said. "To the extent the government pursues an anti-trust case, we think GOOG would be well served to offer up some easy concessions."
However, he did identify a number of risks the company will still face in 2020, including "prospective anti-trust actions given perception that GOOG is a monopoly in search/requires them to change business practice."
Correction: This story and headline have been updated to reflect that Facebook's stock hit a 52-week high on Monday, not an all-time high.