'have been overrepresented' is correct and is used in written English.
You can use it when you want to describe a situation in which a certain group or concept is given a higher prominence in a particular context than it normally would have. For example: "Women have been overrepresented in popular media for a number of years."
For many years, notes Alex Piquero, youth of color have been overrepresented at every stage of the U.S. juvenile justice system.
This might seem plausible at a first glance because in most Western countries migrants have been overrepresented among the working class.
Out of 346 patients 152 (44%) had a mean co-medication period of 22.4 out of 52 weeks (see Table 2), which indicates that patients with a severe course of illness were unlikely to have been overrepresented.
Further, since World War I, when the U.S. mobilized Puerto Ricans en masse for the first time, they have been overrepresented in the military.
Moreover, it is possible that animals from some regions have been overrepresented in our sample.
Therefore, counties with a large percentage of small flocks (<20 ewes) may have been overrepresented.
Traditionally, particularly in the South, the populations of rural areas had been overrepresented in legislatures in proportion to those of urban and suburban areas.
We also avoided one conspicuous species of ostracod (large-bodied, blue morphospecies) which had been overrepresented in previous analyses.
The authors withhold their own opinions through most of the book, but it is clear they believe that, with notable exceptions, the N.Y.P.D. has until recently been run by fools, and that maniacs and men of violence have long been overrepresented in the ranks.
Non-whites in metropolitan St . Louishave been far overrepresented in low-paying civil service jobs.
Young people from relatively prosperous, educated backgrounds have long been overrepresented in jihadist causes.
