Last week the actors' union Equity published the results of an online survey on being 'out' in the entertainment industry. It was picked up by The Stage and The Guardian among other publications in articles that quoted positive statistics on the percentage of gay, lesbian and bisexual actors 'out' in their professional lives (81%) and the percentage of actors who are honest about their sexuality to their fellow performers (94%).

Less encouraging statistics from the survey were reported too: that only 57% of respondents list their agent as someone with whom they are honest about their sexuality; that 35% of actors surveyed have experienced homophobia at some point in their professional lives; that 61% of respondents feel being openly gay might restrict the roles available to them.

Now, to be clear, I'm really pleased that this issue is getting media coverage – until we can truly say that a person's sexual preference has no effect on their career prospects in this, or any other industry, we need to keep shouting about it – but it's wise to be cautious when it comes to statistics.

Neither The Stage nor The Guardian mention the numbers involved or that respondents were self-selecting. The union has around 36,000 members and contacted everyone for whom it has email addresses (some tens of thousands, hazarded Max Beckmann, the union's equalities officer), inviting them to complete the online survey last autumn. Only 326 people responded and many people skipped several of the questions asked (you can download the survey summary from Equity's website by clicking here).

The trouble with self-selecting surveys (as opposed to ones where respondents are chosen at random) is that the small number who choose to respond tend to feel more strongly (either negatively or positively) than the majority who choose not to respond. So rather than getting a representative sample of the feelings of Equity's gay and lesbian members, a survey such as this will over or under-represent particular experiences. Drawing any conclusions from it must therefore be done with extreme caution, or ideally, not at all.

A more sensible course, and one already advocated by Equity's LGBT Committee, would be for the union to monitor its membership for sexuality, as most UK trade unions do. Equity currently only monitors its members for gender and age and therefore holds no data on the way they break down along lines of sexual preference, disability or ethnicity. The union's argument against additional monitoring is that it would make applying for membership more time-consuming than it already is and might put people off joining, but I think this is short-sighted. One of the most important roles that trade unions play is advocating on behalf of their minority members – surely Equity would be better placed to help its members if it had a clearer idea of who they are?

This post isn't intended as a swipe at Equity, who do great work across a whole range of issues affecting performers and creative professionals, but rather a plea for a more nuanced approach to a complex, emotive topic. If we really want to address the problem of homophobic discrimination in the entertainment industry, we first need to get our facts straight.