The fact that women are vastly under-represented in high-level leadership positions is well-known, but the exact reason for it is still the subject of much debate.
Some speculate that women's maternal instincts mean they simply have other priorities; while the role congruity theory hypothesises that there is greater prejudice toward women as leaders because stereotypically, they aren't thought to possess leadership qualities.
A 1990 study published in the Journal of Personality and Social Psychology demonstrated this stereotype by showing that female leaders were given more negative feedback than male leaders, despite offering identical suggestions and arguments.
Of course, there is plenty of research showing that women can and do make excellent leaders.
A study from Concordia University showed that women possess certain qualities that make them better suited than men to wield positions of power, and a research report in Catalyst showed that companies with three or more women on the board outperformed companies with all-male boards.
Recently, though, we've been seeing another issue highlighted.
A meta-analysis of nearly 100 studies that examined perceptions of female leaders showed that men and women are rated equally when it comes to leadership abilities, and sometimes women are even rated more highly.
However, another thing it uncovered is that when men and women are asked to rate their own leadership abilities, men consistently rate themselves more highly than women rate themselves.
Research has long shown that men are more self-assured in general, and often overestimate their abilities and potential, while women are far more prone to underestimate and second-guess themselves.
In a survey of nearly 3,000 managers published by the Institute of Leadership and Management, half of female respondents reported self-doubt about their job performance and career, compared to only 31% of male respondents.
Research by Cornell psychologist David Dunning and Washington State University psychologist Joyce Ehrlinger also shows that women tend to rate themselves more negatively.
In the study, male and female college students were given a quiz on scientific reasoning, after which they were asked to assess how many questions they thought they had gotten right. On average, the male students thought they had gotten 7.1 answers right, while the female students thought they had only answered 5.8 correctly.
In reality, though, the average for male and female students was almost exactly the same - 7.5 correct answers for the female students and 7.9 for the male students.
This negative self-perception can prevent women from taking on new challenges or opportunities, as the researchers demonstrated by inviting the same students to participate in a science competition for prizes after completing the quiz.
Despite having no knowledge of how they had performed, the female students were more likely to turn down the opportunity. Only 49% of them signed up, compared to 71% of the male students.
In their recent book The Confidence Code, BBC World News anchor Katty Kay and ABC News reporter Claire Shipman discuss this so called "confidence gap."
They explain that confidence is just as important to success as competence, so a lack of confidence can cause women to opt out of careers in non-traditional industries, prevent them from pursuing promotions, and even cause them to attribute their successes to good luck rather than skill or hard work.
Dr. Elizabeth Lombardo, psychologist and author of the book Better than Perfect, believes that perfectionism is another thing that often holds women back and causes them to doubt themselves.
"So many women today have a perfectionist mentality," she says. "They think it has to be perfect or why even bother?"
What's more, adds Lombardo, women often joke with their friends, by putting themselves down. But even if they don't truly believe what they're are saying, the subconscious absorbs those negative comments and takes them as truth.
So what should we be doing about it?
Lombardo suggests ditching the "all or nothing" mentality and speaking more positively about ourselves, both in front of others and when alone.
"We are all better at some things than others, so focus on what you enjoy doing and what tends to come more naturally," she says. "Develop and use those skills to your advantage."
"Also, try to reframe the concept of failure. Look at it as data; something you will use to make a smarter decision in the future, to advance, and to get you to where you truly want to go."
Another thing that can boost confidence is pushing the boundaries of our comfort zone. "Persistence is a vital ingredient to achieving what you want in life, and it involves stepping outside of your comfort zone," Lombardo says.
She explains that people often associate discomfort with meaning that they shouldn't do something, when in reality anything new is going to feel awkward at first. So instead of shying away from things that feel uncomfortable, we need to remind ourselves that it's just a normal part of developing a new skill.
"The more comfortable you get with being uncomfortable, the easier it will become. Look for opportunities to practice this wherever you are," she says.
For example, if you don't normally speak up in a restaurant when a waiter forgets part of your order, make an effort to politely remind him. If you don't like to speak in front of a group of people, start by raising your hand in meetings and sharing the things that are important to you, even if it makes you a bit nervous.
Of course, confidence alone doesn't guarantee anything, and as Guardian columnist Jessica Valenti recently pointed out, the "confidence gap" is not a personal defect as much as it is a reflection of a culture that gives women no reason to feel self-assured.
She notes that if we truly want women to be more confident, we need to create a culture that values self-assured women.
However, if a lack of confidence is discouraging women from trying at all (and research shows that it does), then it stands to reason that boosting confidence could be at least part of the solution, because although greater confidence doesn't guarantee success, inaction certainly guarantees failure.