Hemiptera plant. Phloem sap, which has a higher concentration of sugars and nitrogen, is under positive pressure unlike the more dilute xylem sap. Most of the Sternorrhyncha and a number of Auchenorrhynchan groups feed on phloem. Phloem feeding is common in the Fulgoromorpha, most Cicadellidae and in the Heteroptera. The Typhlocybine Cicadellids specialize in feeding on non-vascular mesophyll tissue of leaves, which is more nutritious than the leaf epidermis. Most Heteroptera also feed on mesophyll tissue where they are more likely to encounter defensive secondary plant metabolites which often leads to the evolution of host specificity. Obligate xylem feeding is a
Sugary drink tax a targeted tax on sugary drinks at a national level in 2012; following introduction, soft drinks are estimated to be up to 3.5% more expensive. Analysis by the market research firm Canadean found that sales of soft drinks declined in the year following the introduction of the tax, following several years of annual growth. However, the tax applies to both drinks with added sugars and drinks with artificial sweeteners, possibly limiting its effects on the healthfulness of soda products. A 2016 study by Mazzochi has shown that the sugary drinks tax saw a 19 euro-cent per liter increase in price