Yes, it's the associate attorney:
“Associate attorneys stated they felt most unhappy with their company culture. . . In many cases, law firms are conducted in a structured environment that is heavily centered on billable hours. It may take several years for an associate attorney to rise to the rank of partner. People in this position rated the way they work and the rewards they receive lower than any other industry.”
Based on what my friends in Biglaw say, that sounds about right.