What's the lowest ratio of oil to vinegar that you can use in a vinaigrette?

Thanks to the assistance of a smart food blogger, who saw immediately EXACTLY what I was asking, and knew how to phrase it to show that I'm NOT asking for opinions, I now have the following revised phrasing of the question:

In order to have a proper vinaigrette, that doesn't separate back out 5 seconds after you mix it, it needs to be EMULSIFIED. Let's assume that we're talking about a standard emulsifier for vinaigrette; ½ teaspoon of Dijon mustard per tablespoon of vinegar.

The goal is to get the vinaigrette to STAY emulsified for some reasonable amount of time, in other words, to create a STABLE emulsion. According to one major site, "Properly emulsified dressings will stay mixed for at least a day or two in the refrigerator."

https://www.allrecipes.com/article/how-to-emulsify-vinaigrette/

As you lower the ratio of oil to vinegar in a vinaigrette, it gradually becomes more difficult to emulsify, eventually reaching the point where it is no longer possible to form a STABLE EMULSION. Assuming access to normal home equipment and ingredients only, in other words no industrial mixers or chemicals, at room temperature, what is the lowest proportion of oil to vinegar at which a STABLE emulsion can be produced?