Generation Y is a marketing concept – and not much more. It allows advertisers to define a group of people, but the evidence for extending and attributing behaviours to this group is wafer thin. But this is what's happening: because this generation has access to certain lifestyles and opportunities, it's suddenly become a case of assuming we all behave and think the same way. Chelle Johnson slips into the trap of assigning personality traits to Gen-Yers on top of their media consumption habits, but these assumptions seem to me to be inherently wrong. My own traits are probably more similar to my grandfathers' (one police sergeant, one slaughterman, both Scottish and dead) than to, say, Dizzee Rascal's.

To ascribe hopes, dreams and values to a group of people who only have a birth period in common is senseless. Generation Y-ers are taken to have been born between 1980 and 2000, which raises the first ridiculous point of this category: someone born in 1983 (age 27) is not going to have much in common with someone born in 1998 (age 12) beyond their number of knees.

What am I, as a Gen Y-er, supposed to be like? Well, apparently I'm a voracious adopter of new technology (even though the 35-54 age group is the single biggest population of Facebook, and there are more Twitter users over the age of 30 than under it).

I'm told that I want a job I'm passionate about (which presumably is why the UK's top five most popular graduate recruiters include three accountancy firms and a budget supermarket known for paying high salaries. I guess it's also why those immoral investment banks still easily recruit young people).

I'm supposed to be a bit dim and not live in the real world (I promiss I can spllez fings write, and have a basic grasp of the concept of 'the world').

I have the reputation of being less loyal as an employee (though I don't know how they came to that conclusion about me, because I've only had one job since leaving university and starting a "career" – my Gen-Y cohorts have only been in the workplace for a decade or so, and 90% of that time was spent in a massive economic boom with plenty of jobs for those with the available skill).

The media paints me as cynical and brand-aware (in other news, Topshop continues its march to world domination and Nestlé continues to turn a profit), and I care about the environment (though has anyone ever said no to the question, "do you care about the environment?").

The last point is particularly salient: it highlights that the questions Gen Y-ers get asked during such a market research are thought up by the over-30s. Marketers become aware of a hot issue, and therefore ask Gen Y-ers about it. Thirty years ago, no-one ever asked "is it important to you to work for an environmentally responsible employer?" But it doesn't much matter: getting a good job is the number one priority for graduates. Researches are also skewed in other ways: it is graduates that attract the overwhelming majority of attention. No-one seems that interested in finding out about the attitudes of non-grads compared to their middle-class contemporaries. The arrogance of assuming the middle classes are indicative of everybody!

We're all going to know plenty of Gen Y-ers who don't fit the stereotype and plenty of non-Gen Y-ers who perfectly do. That's because we're far more than just a product of our time. Sure, we're influenced by the media, available technology and economic conditions, but geography, our friends and families, personal wealth and our heritage all contribute far more to our personalities than our date of birth. A specific historical context may influence our actions, but it doesn't necessarily influence our moral codes. A generational age bracket is not an indicator of personality – as demonstrated by the most accurate quote I've ever seen pertaining to Gen Y-ers' career hopes:

"The contempt of risk and the presumptuous hope of success, are in no period of life more active than at the age at which young people choose their professions."

That was written by Adam Smith in 1776. Let's not assume we're special.

• The author posts on Cif under the username unexceptional