Science may be an accurate process of finding the truth, but scientific publishing is imperfect in many ways. It’s not just that scientists aren’t paid for their work despite how much accessing peer-reviewed research costs (though that’s a big problem), but according to a new study, there’s also a bias problem. Specifically, researchers from richer countries tend to receive more attention than those from other countries.

When researchers write scientific papers, they cite previous works to justify their assumptions, and design, or to explain why they did the study the way they did it. It’s a common process, and most papers will have dozens of citations. Citations are so ubiquitous in science that they themselves are studied to better understand the flow of ideas between researchers, different fields, and countries.

A trio of researchers from Queens College, City University of New York, the University of California, Los Angeles, and Stanford University wanted to see how the flow of citations varies for researchers in different countries. They analyzed nearly 20 million scientific papers from 150 fields over the years from 1980 to 2012.

The researchers found a strong citational bias in research papers. Basically, some countries are simply overcited — countries like the Netherlands, Switzerland, or Germany. Meanwhile, countries like Mexico and Brazil received fewer citations in general. The researchers also found that the bias is increasing in recent years.

“Much like how gravity distorts our perception of light, national factors distort our perception of international science,” the study reads.

Rich countries tend to host the best universities, the most Nobel laureates, and the most journal editors, so knowledge production is skewed towards these resource-wealthy constructions. But identifying undercited countries promotes the inclusion of underheard voices. Keeping these voices out of the scientific conversation is not only bad from an ethical perspective but also counterproductive scientifically.

“We find that scientific communities increasingly centre research from highly active countries while overlooking work from peripheral countries. This inequality is likely to pose substantial challenges to the growth of novel ideas,” the researchers note.

“The type of distortion we consider here is also likely to be problematic for scientific progress if knowledge remains unincorporated and human capital unused,” they add.

It’s not the first time this sort of bias has been uncovered. Previous research has also found that men tend to be overcited, while women tend to be undercited. For science to truly become inclusive

The study was published in Nature Human Behavior.