As altitude increases, the available amount of oxygen to sustain mental and physical alertness decreases with the overall air pressure, though the relative percentage of oxygen in air, at about 21%, remains practically unchanged up to 21,000 metres (70,000 ft).
  State legislators in Texas (both representatives and senators) make a salary of $7,200 per year.
In total, 12 senators and 36 representatives fit into this category and each earned $74,779 last year. With only 40 senators, virtually every member of that body held either a leadership or a committee position that resulted in additional pay in 2013. In the 160-member House, 60 members earned at least $74,000 in 2013.