Movies and wines also share something else in common; ratings. Before you go to a movie, you may have watched a movie critic on TV or read a review on the web. Sometimes you know the director from previous movies, so you have a good idea of what style and quality to expect. Similarly with wine. Many people will read online reviews or a review in a newspaper before purchasing their bottle. In some cases you may have a favourite winery or wine maker, so you know when you find a bottle by that winery or wine maker, regardless of vintage, that you will likely enjoy that sip.
Let’s get back to ratings. They can make or break a movie or a wine; especially if it is by a well-known critic.
How Are Movies Rated?
1.5 Mainly boring some but awful parts
2.5 Not worth watching
3.0 Watch once
3.5 Worth watching twice
4.0 Well done
4.5 Very well done
There are many variations, but the theme is going from worst to best. If you watch a comedy or a romance movie, and someone says it is 3 stars, you can have a good idea of the quality, even though both are a different type of film. You can even easily swap the star value for the descriptor and the rating would still make sense to you.
This type of scaling is known as “ordinal”. It is a subjective scale, and even though you cannot make absolute numerical differences, we can still get a good idea of how wonderful or pathetic a movie is by such a scale. Let’s move to wine ratings.
How Are Wines Rated?
You rarely see a star rating, unless you are mywinepal (Read mywinepal’s 5 star rating here). Most wine critics use the 100 point scale, which people hold very dearly. Some people for example, only purchase wines that have been rated as 90+ points. And some wineries, if they get this level of rating, may decide to boost the price of their wine. But what most people do not understand when they hear of a 100 point scale, is that the scale does not start at zero. It starts at an arbitrary value of 50, and the quality of a wine at that value is ill-defined.
A scaling system that starts at zero, is known as a “ratio” scale, and has mathematical properties, such as 20 is 2x greater than 10. With a numeric scale that does not start at 0, you cannot say that a 80 point wine is 33% times better than a 60 point wine. But people do not realize that; they grade the ratings very finely and think that they are adding more precision than is warranted.
Try this. Write a brief description of how you would describe a 89 point wine and a 90 point wine. Difficult, right? I would probably enjoy an 89 point wine as much as a 90 point wine, and save a few dollars at my local bottle shop. But what does this have to do with movies?
Rating Movies Like Wine
Using the 100 point rating scale, how would movies ratings show? Here are the latest movie ratings from Rolling Stone (who uses a 4 star rating).
- Life, animated 3.5/4 stars
- The BFG 3/4 stars
- Independence Day: Resurgence 2/4 stars
- Free State of Jones 1/4 stars
Let’s scale the ratings to a 100 point system (with an arbitrary 50 starting point).
- Life, animated 93.75 points
- The BFG 87.5 points
- Independence Day: Resurgence 75 points
- Free State of Jones 62.5 points
In the 4 star rating above, one can easily understand that one movie is a bit better/worse than the next movie, but re-cast into the 100 point scale, it is more difficult to tell the difference. In the above scaling example, each 0.5 star = 12.5 points. So going up half a star really makes the point value increase significantly. If you look at wine ratings where they measure 89 vs 90 points, how much of a star difference would that be in the 4 point scaling used by Rolling Stone? 1 point = 0.04 stars! Wow.
That is a lot of precision that I think movie critics would say is impossible to accurately mark. So why do wine critics do it, and we follow? I think that there is a two-fold reason: 1) the critics do not understand the numeric ramifications of a 100 point scale with an arbitrary starting point, and 2) consumers do not know how the scaling works, and assume that it is a quantitative rating that begins at zero.
Hopefully as people learn more about problems with the 100 point scale, there will be a movement to a more statistically valid, ordinal scale rating system, such as 4 or 5 star ratings. Enjoy your movies and wines this summer, regardless of the ratings.