Wikipedia specifies the Mincer equation like this:
$$\ln w = \ln w_0 + \rho s + \beta_1 x + \beta_2 x^2$$
and states that $w$ is wage, $s$ is years of schooling and $x$ is potential experience.
Because it is potential experience, I believe there might be a lot of different interpretations of it.
One possibility that came to my mind is using (age - years of schooling). But one problem with it is that it assumes people cannot work while studying. Another possibility is simply using (age - legal minimum age of employment) or simply age (just an affine transformation of the previous so it shouldn't affect our results), assuming that anyone above the legal minimum age could have potentially worked, regardless of whether they actually worked or not.
How is it actually proxied in the literature? Is there any widely used proxy for this? What are the justifications?