CAM and C4 plants conduct photosynthesis in ways that allow them to live in drier areas than most C3 plants can tolerate. The effectiveness of different plants in restricting water loss while still allowing for influx of adequate CO2 can be compared using the transpiration ratio, which is calculated by dividing the amount of water transpired by the amount of CO2 fixed by photosynthesis. If a typical transpiration ratio for a C3 plant is 500, then possible values for CAM and C4 plants could be