Apply to be an economist for the Census using the generic job-market process for new PhDs (JOE, EJM, etc). After your fly out, you will be asked to apply through USA Jobs. To negotiate a higher salary, it helps to have proof of another standing offer. I got the sense that the interviewers were looking for individuals who not only fit their needs, but would fit well into the climate of office. In my first interview they asked questions about my technical skills, research interests, and how well I can think of new research ideas when put on the spot. My fly out was all about whether I would get along with everyone. It was my most pleasant fly out - no one tried to put down my research during my seminar and everyone was friendly.