Okay, looked at the graph: Copied it to my system clipboard, read it into an old copy of Microsoft Photodraw, magnified it by 400% and THEN could read the axis

Okay, looked at the graph: Copied it to my system clipboard, read it into an old copy of Microsoft Photodraw, magnified it by 400% and THEN could read the axis annotation!!! The horizontal axis is time and goes from 1965 to 2017. The vertical axis is "global" natural gas volume demand in units of a billion cubic feet per day (at standard temperature and pressure, likely, hopefully). In 1965 the volume was about 60. In 2017 the volume was about 370. Between these two points, the graph went "up and to the right"! So, since 1965, the volume is up by a factor of about 6. Not wildly surprising. I grew up in west Tennessee, and the winter heat was from natural gas. Recently I returned to Tennessee, east Tennessee, and again the winter heat is from natural gas. Cozy!!! Between the two, I was long in NY with winter heat from fuel oil: Messy, had to have the furnace cleaned, and the oil was from a delivery truck -- botheration. Tennessee seems to do well on energy: There's the natural gas -- I have no idea where it comes from. There's TVA with hydropower from the Tennessee River. When demand for electric power grew, IIRC they used nuclear fission and coal. Maybe now they are using natural gas. Of course, in east Tennessee is Oak Ridge with a long history in energy generation and now supercomputers. I like Tennessee!