You are not mistaken; the level of alcohol in wines has been steadily increasing for the last decade or more. The reason for this is quite simple, at least in part; climate change.
As grapes ripen, their sugar levels increase. When the grapes are picked, crushed and fermented, those sugars turn into alcohol. So, the more sugar in the grapes, the more alcohol in the finished wine. As many wine regions have become warmer, so the alcohol levels of the wines have increased. Bordeaux is a perfect example. Back in the 1960s and 1970s, most Bordeaux was between 12 per cent and 13 per cent abv. Nowadays, it is not unusual to find wines with 14 per cent or more, with many hitting a heart-warming 15 per cent.
This is partly down to climate change. An increase of one degree centigrade can make a huge difference to ripening grapes. In addition, during the same period, growers learned to farm better, reducing yields and harvesting at optimal periods. All of this meant riper grapes with more sugar.
Wine can vary in alcohol from as little as 5 per cent to 25 per cent abv. Lower alcohol wines can be made in three ways. The grower can pick their grapes early, before the sugars have had a chance to increase. This will make for a lighter but probably quite acidic wine. Alternatively, a producer can stop the wine from fermenting halfway through. This will leave the wine tasting a little or very sweet. German wines such as Mosel Riesling and Italian sparkling wines such as Moscato d’Asti are made this way. It is also possible to reduce wine after fermentation by vacuum distillation, reverse osmosis, or spinning cone. All three of these will lower alcohol levels but may also affect the taste of the wine.
Any wine with more than 15 per cent abv will usually have been fortified, or had brandy added. This is the way sherry, port, marsala and madeira are made.
Wines with high alcohol are not necessarily a bad thing, although it does mean you should drink them in smaller quantities. But wine is about balance and both a good Mosel riesling, with an abv of around 8 per cent, and a fine old oloroso sherry at 20 per cent are among the greatest wines of all.
In the European Union, all labels must state the alcohol content of the wine. Producers are allowed a 0.5 per cent tolerance one way or the other (0.8 per cent with older wines), so your 13.5 per cent wine may actually be 14% or 13%.
