Let's look at some of the best practices first.
Lean Six Sigma is an exponential improvement methodology that results in breakthrough improvements. To help realize its transformative power, the improvement goal should be a stretch goal. Typically, a stretch goal would imply at least 50 percent improvement over the current performance. An example could be if the current productivity level is 15 units / day, the improvement goal should be at least 23 units/day (about a 50 percent improvement).
Benchmarking against the competition can be another very powerful way to set a proper stretch target. Benchmarking refers to the process of comparing the existing process and performance metrics with that of the best in the industry or the best practices from other industries.