In an economics thesis, the introduction is typically 15-20 pages long and consists of a brief summary as well as collation of the substantial articles of the thesis. This means the introduction should explain what the main findings of the thesis are and justify why they belong together in the same thesis. The introduction should also discuss any challenges related to research ethics and theory of science that the research for the thesis raises.
The thesis, excluding the introduction, should be the equivalent of three journal articles of ordinary scope, where one is single-authored and the other two have no more than one co-author each.
Three articles might be sufficient even with more co-authors than this, as long as this is compensated by one article in the thesis being a so-called job-market paper, i.e. having a larger scope than an ordinary article.