Demographics are the cold hard facts about a population. We tend to group people based on factors they share;
Depending on what you are selling these may be more or less relevant to you. If they bear no relevance then there is no need to include them but I’d suspect some will. We will consider each in detail.
Sex
This will really only matter if your product or service links to physical parts of a human that only certain humans have. A typical example would be sanitary products that are only relevant to people who have periods. You might be raising awareness of prostate cancers and therefore target people who are male because they have a prostate.
Gender
You might target products based on gender. Clothing typically is split into menswear and womenswear. Bras tend to be used by women. Fitness services are sometimes targeted at a gender group. Please also consider the transgender community or those who are non-binary, if there is no legitimate need to segment based on gender then don’t.
Age
Alcohol is a prime example for choosing your age demographic carefully. Selling whisky to 5 years olds is generally frowned upon and often illegal. Regardless of what you are selling there is most likely an age range below which and above which the probability of them being interested diminishes.
When we are considering any segmentation it is true that anyone could buy. However we are interested in the most likely people to buy and excluding those where the probability is lowest. It’s worth thinking about each of the demographic segments in terms of, what is the percentage chance a person of this demographic segment will buy my thing (all other things being equal.)
Race
Is your product or service focused on supporting people with a race related problem? If it is then I would suggest including this demographic in your ideal customer profile. For example black mothers in the UK are more at risk of dying during pregnancy and childbirth than white women. In that instance race is very relevant.
Martial Status
Did you know the number one cause of divorce in the UK is getting married? Divorce lawyers would do well to focus on people who are married rather than single people. And marriage guidance counsellors would too. Some products (hopefully) only matter if you are single on the other hand, dating websites in the main.
Education level
If you are selling a Masters programme you want people who already have an undergraduate degree.