Do not leave the reader thinking "So What?" after reading your thesis! Your goal is an exemplary thesis statement and an exemplary thesis is complex.
To determine whether your thesis is simple or complex ask the following:
Is it debatable?
 

• A simple thesis proves an obvious, non-debatable idea.
• A complex thesis proves a fresh, debatable idea.

• A simple thesis rests with easy answers.
• A complex thesis explores difficult territory.

• A simple thesis repeats the same idea.
• A complex thesis progresses through several steps.

• A simple thesis doesn't matter.
• A complex thesis matters