The forces against you are not all linear. At "higher" speeds, wind resistance dictates small gaps between gears whereas going slowly, the forces are linear and the gearing gaps should be larger. To double your speed, the wind resistance is 8 times higher or more realistically, a 10% increase in speed when riding "fast" requires about 30% more power. On a steep hill, 10% increase in speed only requires a 10% increase in power. So, a corn cob at one end and big gear jumps at the other. SRAM's 10-33 or Shimano 11-30 12 speed pared to the right chain rings for your preference would be about as close to "linear" as you can get.