It is more important to look at drinking patterns and reasons for drinking. Someone who is clearly drinking to relieve stress is to be considered a potential alcoholic. While some people may think it is fine to have a few beers after work and blow off some steam, it can also be a sign that your spouse is unable to effectively deal with job difficulties and needs the outlet of drinking to diffuse the situation. The same goes for someone who heads to the bar after a fight with their spouse. This can also become a pattern, a form of escaping reality.
Alcoholics also tend to have certain personality traits.
They tend to blame others for things that go wrong. Responsibility becomes something they do not want to accept and would rather put on other people. For a marriage in trouble, it is often the alcoholic who accuses the other for something gone wrong rather than accept their drinking might be the real heart of the issue. Look at your own involvement in drinking as well. This may seem like an effective way to control the situation but the drinkers need to control it themselves.