Google +, Google’s new social network, was launched last month to much fanfare as an invitation-only service.  According to early data, membership in the first few weeks was a much as 90% male. Now it’s more like a 75/25 split – better, but nowhere near parity. A popular meme earlier this week compared the service to a group of men sitting around in a hot tub without a female in sight.

A quick look at users’ occupations and an answer for the imbalance begins to take shape. The top four most popular jobs for users of Google + are Engineer, Developer, Designer, and Software Engineer – all notoriously male-dominated – with a total of nearly 60% of the network’s membership and an average of 91% men. The only jobs in the list of users’ top 30 occupations that have a majority of women are Librarian, Nurse and Wife.

Now before we go any further, it’s worth noting that I’m not a statistician, but even I can tell you this data is neither an entirely accurate nor even a necessarily representative reflection of Google + users in real life. (Of the 235 people who identify their occupation as “Wife,” 22 are men.) Still, it does provide an interesting, if skewed, look into gender and technology.

The effect of Google + being an invitation-only service is that the earliest adopters have been largely hardcore techies and Google employees, both elite and primarily male groups. (Presumably – Google has refused to release information on the race and gender of its employees, citing the prerogative to protect “trade secrets”) It only makes sense that these men, when given the opportunity to invite others into the service, started out by inviting their friends. It also makes sense that their friends happened to look like them.

In fact, the tendency to favor members of one’s own perceived social group is a well-known phenomenon in social science, called in-group favoritism. In the case of Silicon Valley, it’s a vicious cycle. In the real world as in the virtual world, gender imbalances are often self-reinforcing: once a particular skill set (like math), job (computer programmer), or interest (technology) has been gendered male, success at the relevant skill becomes implicitly linked to being male. When you think about a computer programmer, you see a pale, skinny, bespectacled man.

Once that paradigm has been established, it leads to in-group favoritism. Studies show that people hire employees who belong to their social group, perceiving them – mostly unconsciously – as more qualified and less risky than someone else with identical qualifications. In fact, hiring friends of current employees is a central part of Google’s recruiting strategy: employees are offered a several thousand-dollar bonus if someone they refer to the company is hired. In other words, the best way to get one of the most coveted jobs in the world is to know someone on the inside who thinks you’d fit in. It’s just a new twist on the old boy’s network. And the results are the same.

When it comes to Google + the issue of the gender imbalance seems likely to be a temporary one. While for now membership is still invitation-based, invitations aren’t that hard to come by, and there are already upwards of ten million users.

But the underlying problem isn’t so easy to solve. The thing is, there’s always a limited number of invitations into the elite. That’s kind of the point. So until we take a good hard look at the New Boys’ Club, the tech world is going to look like Google + in its first few weeks. And no one wants to be in a hot tub full of guys.

(data on Google + taken from http://findpeopleonplus.com/statistics#stat_gender)

Rachel Dempsey is working with Joan Williams on an upcoming book about gender bias in the office.