Women head up just 33 of the United Statess 500 highest-earning companies in 2019, as MeToo and boards boost numbers.

More women are heading up top-earning companies in theUnited Statesthan ever before, according to an annual study by a leading business magazine.

Fortune magazine released its 65th annualFortune 500list on Thursday, reporting that female CEOs will lead 33 of the USs highest-earning companies by June 1.

While the number reflects a tiny proportion of the full list – just 6.6 percent – its a notable rise from last year, when the number of companies headed by women dipped to 24, following the departures of prominent female executives such as PepsiCos Indra Nooyi.

Id love to say Im ecstatic about this number, but its still way too low, said JenniferFloto, a professor at the University of Southern Californias Annenberg School for Communication and Journalism.

I entered the corporate world in 1973 and would have expected this number to be close to 50/50 in 2019. But, it is a step in the right direction, she told Al Jazeera.

Susan Fleming, a former professor at Cornell University who sits on the boards of several companies, was cautiously optimistic about the figures.

Its encouraging and its definitely positive, but I dont think it suddenly means that its going to keep increasing dramatically,she said.

This years rise was driven by women being appointed as CEOs in the last year and by companies with female CEOs making enough revenue to gain a place in the list. But other factors have also had an influence on new appointments.

Activism has played a role, according to analysts, who see the effects of theMeToomovement in the record number of male executives changing positions due to ethical – rather than financial or performance-related – issues.

In facing up to charges of sexual harassment in the workplace, companies are being forced to redress inequality within their teams, Fleming said.

I think there is more sensitivity and thought about gender equality because sexual harassment at the end of the day is about power and dominance over others, and so if youre going to take on issues like sexual harassment, youre also going to have to take on gender equality.

That doesnt mean that theyre going to go out and pick a woman to have a woman CEO, but that theyre maybe going to look a little harder and a little more broadly at the pool of people theyre considering, and theres tonnes of amazing women out there, she told Al Jazeera.

Perhaps the biggest driver of change is the incremental increase of diversity on boards at top firms.

White men appoint other white men; women have to prove themselves for much longer before being invited in. So its logical that once women and other underrepresented groups finally get a seat in the C-suite – and subsequently on boards – they will open others eyes to the advantages of diversity, Floto said.

Were slowly showing our children that people of any race or gender can be effective leaders when given the opportunity.

Another takeaway from this years list is that the USs biggest businesses are getting bigger – and its richest are getting richer.

Together, the companies included in the list – titled The Price of Size – raked in $13.7 trillion in revenues. But just a tenth of the companies accounted for nearly half of that figure.

Some 27 companies earned at least $10bn in the last fiscal year, while six have at least $1 trillion in assets on their balance sheets, according to Fortune.

There was little change at the top of the list, with Walmart holding onto the number-one spot and ExxonMobil coming in at number two. The energy giant is among 53 companies to have appeared on the list every year since its debut in 1955.

Tech giantApplemoved up a spot to number three, pushing Warren Buffetts Berkshire Hathaway hedge fund down to four, while Amazon made the biggest jump inside the top 10, rising three spots to number five.

Pharmaceutical distributor AmerisourceBergen, which is under scrutiny for its alleged role in theopioid crisisgripping the US, made its first appearance in the top 10 in this years list, boosted by a rise in prescription drugs prices.

Other trends saw several large home builders leaping up the list, with Lennar and Toll Brothers rising 76 and 52 places respectively on the back of a housing boom.

Companies from the energy and oil sectors also continued to make a strong showing, with Chevron, Phillips 66 and Valero all making gains.