From "Analysis of Reserve and Regular Bottlings: Why Pay for a Difference Only the Critics Claim to Notice?" Published by Roman Weil, Co-Chairman, Oenonomy Society of the US, 2013.05.16. Emphasis mine.

The wine maker harvests the grapes, sorting the best from the ordinary. At the end of the harvest, the pile of ordinary grapes exceeds the size of the pile of the best grapes, often by a factor of more than five. The wine maker takes special care in turning those best grapes into wine, bottles it separately, labels it differently, calls it the Reserve Bottling, to distinguish it from the bottling of wine made from the ordinary grapes, and offers it for sale at a price from as little as 40 percent higher to as much as three times the price of the regular bottlings. The process of sorting ordinary from best may involve the wine maker's selecting barrels of grape juice after the press or after some aging, or from sorting wines grown on one plot differently from another plot. One way or another, the wine maker distinguishes regular wine from similar, putatively great wine, with a reserve designation, perhaps using a different word, but the same concept.
Here, I report my tests of wine testers' ability to distinguish reserve bottlings from regular. My results show that:
just over 40 percent of my wine tester subjects can distinguish in blind tastings the regular from the reserve versions of a wine, whereas one-third could if the process was random, and
of those who can distinguish, half prefer the reserve and just under half prefer the regular.
Conclusion: Wine drinkers cannot distinguish much better than chance between regular and reserve versions of a wine. Those who can distinguish the difference do not prefer the more expensive reserve except at random. In only a fifth of the tests could the tester both distinguish the regular from the reserve and prefer to drink the more expensive reserve.

Later, on the experimental methods:

Most of the testers were either MBA students at the Graduate School of Business of the University of Chicago or its alumni, alumnae, and their companions. They are primarily upper middle-class, experienced and enthusiastic wine drinkers, but not experts. All testers paid an entry fee for the testing, which fee covered full costs of the testing, and in the case of some of the alumni, more.

And later still:

What to do with these results? ...If you serve the reserve wine, be sure to show your guests the label, because the chances are four to one against any one person's being impressed by the taste, so that any warm feelings the guest forms of your generosity will likely come from visual, not olfactory and taste, stimuli.