Demographics
The Google Display Network offers several categories of demographics: gender, age, parental status, and household income. These are not as accurate as you might expect, but they get the job done.
Gender
Google has broken gender into Male, Female and Unknown categories. You might expect that Unknown will be a small percentage of your target audience, but in my experience, this is usually just someone that hasn’t selected a gender when creating a Google account. While Google has thousands and thousands of pages worth of data points on each of us, the optics of gender are such that Google prefers to use Unknown rather than assuming genders.
Age
‘Traditional’ ad buyers are probably accustomed to seeing age targeting options. Google has broken them out into 18-24, 25-34, 45-54, 55-64, 65+, and ‘unknown’. Google wisely won’t let you directly target those under 18 years of age, and you also can’t target individual ages.
Take ages with a grain of salt, and don’t’ exclude Unknowns without a good reason. When I signed up for my first Google account in 2004, I chose the oldest possible birthday, and (on paper) Google may claim that I’m well over 115 years old. Given all the data Google has on me, I don’t think that’s the case…but take these ages with a grain of salt.