TIOBE bases its rankings on data from a variety of aggregators and search engines, including Google, Wikipedia, YouTube, and Amazon. In order for a language to rank, it must be Turing complete, have its own Wikipedia entry, and earn more than 5,000 hits for +”<language> programming” on Google.
Although scripting languages are enormously popular (Python, for example, places fourth on November’s list), TIOBE believes that scripting languages are too prone to errors that only show up during run-time, making them a bit too problematic for high-pressure development environments where failure is not an option.
TIOBE’s analysis aside, it seems unlikely that scripting languages as a category are going anywhere: many are easy to learn, even for neophyte programmers, and feature a layer of abstraction that hides many of the thornier aspects of development. And as long as end-users continue to use these languages to construct a wide variety of apps, they’re unlikely to fade away—errors or no.