B.C. Olive trading routes grew up, and gradually Tuscany's landscape took on its silver-crowned appearance. In certain tragic years, frost devastated crops and trees, such as in January 1985, when it seemed that a changing environment menaced the future of olive cultivation. Luckily this was not the case, but this sector of horticulture was nonetheless affected. Up until the early 1980s, 30,000 tons of oil were produced per year, but today the figure is closer to 24,000 tons. 1995 was a particularly good year: Tuscany accounted for over 19 percent of the national production of 123,500 tons of olives. The province of Florence produces 30 percent of Tuscan olive oil, followed by Grosseto, Arezzo, Siena and Lucca. Tuscany's olive trees are not all the same. 80 percent of the trees belong to four varieties, Frantoio, Leccino, Maurino and Puntino (also known as Punteruolo or Trillo); the remaining 20 percent is made up of various other cultivars, including Picholine, of French origin. But in any case, the result is always that exceptional amber liquid, once considered as unhealthy but now returned to its rightful place by today's enthusiasm for the so called Mediterranean diet. There are eight classes of oil: the top is of course "extra vergine", in which the acid content is less than 1 percent, followed by "sopraffino vergine" (under 4 percent acidity) and then, in order, fino vergine, vergine, olive oil, olive and husk oil, rectified olive oil, rectified husk oil. The best way of testing oil quality is by tasting it, poured onto a piece of white bread.