Here's why:

* Aerobic respiration requires oxygen to break down glucose completely into carbon dioxide and water. This process yields a large amount of energy, specifically 36-38 ATP molecules per glucose molecule.

* Anaerobic respiration occurs in the absence of oxygen and only partially breaks down glucose, producing 2 ATP molecules per glucose molecule. This is significantly less energy than aerobic respiration.

Therefore, aerobic respiration is much more efficient at energy production than anaerobic respiration.