Its plain meaning within the context of PERM EB-2 (Bachelor Degree + 5 years of progressive work experience) adjudications is relatively simple: employment experience that reveals progress, moves forward, and advances toward increasingly complex or responsible duties.
In short, progressive experience is demonstrated by advancing levels of responsibility and knowledge in the specialty.
As such it is necessary that your documentation of prior experience either reflects ever increasing responsibilities reflected in promotions to different positions within a company or attainment of an expert opinion letter that reviews your prior positions at a variety of companies to show the progressive nature of your employment history.
Additionally, the employer should be prepared to provide plain-English explanations of the experience required, indicating why five years of post- baccalaureate and progressive experience would be necessary to perform successfully the duties set forth in highly technical job descriptions.
The statement should be an affidavit from some person within the petitioning firm who has relevant knowledge concerning the minimum acceptable qualifications for the position involved in the Form I-140.
It is incumbent upon the petitioner to describe the position offered in such a way so that an adjudicator can reasonably determine whether the job actually requires an advanced degree or, in the alternative, five years of post-baccalaureate experience that is progressive in nature.