I am currently reading a research paper on obfuscation. Here's the portion of the paper that relates to my question.
"while current obfuscation schemes elevate some islets of static analysis, such as changing layout of the source code, changing control flow, and modifying data, they are easily exposed to reverse engineering analysis due to a lack of API concealment. Therefore, a quantitative evaluation scheme is needed to ensure that obfuscation is applied to an appropriate API with an adequate degree of resistance to reverse engineering."