Mercurey Rising?

There’s no doubt that alcohol levels in wine have been rising. But why? Some argue that global warming is to blame. Warmer temperatures mean fully ripe grapes. Fully ripe grapes mean more sugar in the grapes. More sugar in the grapes converts to higher alcohol in the wine during fermentation.

Thanks to Decanter, I recently came across a paper from the American Association of Wine Economists – I bet they have no trouble getting volunteers for field research – that blows a hole in that argument.

Entitled Splendide Mendax: False Label Claims about High and Rising Alcohol Content of Wine, the authors ─ all come from the University of California, Davis except for George Soleas, who is the VP of Quality Assurance and Specialty Services at the LCBO ─ analysed climate data from 1992-2009 and the alcohol levels in over 129,000 samples of wines from around the world.

According to Decanter,

The research indicates, the authors say, that the average alcohol content in wine has increased by 1.12% over 18 years, from a mean of 12.7%...This, they say, is considerably higher than would be expected when set against the heat index, which predicts an average rise of 0.05% in alcohol per year...The study also found discrepancies between alcohol content stated on labels and actual content in bottle. In 57% of the samples, the alcohol level was understated with the worst offending being New World red wine, which averaged 0.45 percentage points [above] the stated level.

Why would that be?

• Winemakers may be chasing the perception that famous critics, and the consumers who follow them, prefer the sensation of higher-alcohol wine.
• Even though consumers prefer the sensation of higher-alcohol wine, they are averse to buying wines with a high level stated on the bottle.
• In some jurisdictions, they tax higher-alcohol wine at a higher rate than lower-alcohol wine. For example, the US federal wine excise tax is higher once a wine passes 14% ABV.

In their conclusion, the authors state,

[W]e have suggested that the substantial, pervasive, systematic errors in the stated alcohol percentage of wine are consistent with a model in which winemakers perceive that consumers demand wine with a [lower] stated alcohol content that is different from the actual alcohol content, and winemakers are willing to err in the direction of providing consumers with what they want. What remains to be resolved is why consumers choose to pay winemakers to lie to them.

Maybe they were drunk at the time?

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