In many research fields, private funding for research is fueling a growing problem, the tendency towards publication bias.
Publication bias is where researchers publish only favorable results, and it can have far-reaching consequences.
Pharmaceutical companies, for example, are notorious for manipulating the data in this way, potentially very dangerous when the lives of patients are at risk.
Unfortunately, pharmaceutical companies are businesses, attempting to maximize profits, and there is always the temptation to promote products, even when they have been shown to be ineffective or even potentially harmful.
The Language Barrier and Publication Bias
Another example of publication bias is caused by language difficulties, where papers written in another language often overlooked.
Famously, medical researchers in the English-speaking world often claimed that there was little empirical research into herbal medicines. This was not quite true, because German researchers have produced reams of papers about herbalism.
Other major languages, such as Russian, Chinese and Japanese are similarly overlooked, and this can have a real and marked effect upon meta-analyzes. With the rise of English as the language of science, as it is of business, such problems are becoming rarer, and major papers are often translated if the original researcher cannot speak English.
The File Drawer Problem and Publication Bias
It is tempting to place the blame for publication bias entirely upon rejection of papers by journals, but this is not always the case. Quite often, researchers are to blame for not releasing negative results.
Often, they do not wish to release negative results, because it may reflect badly on future grant applications, or they are aware of the mistakes that they made in procedure and have no wish to have their mistakes dissected by their peers. In other cases, they may have drifted onto other areas, or run out of funding halfway through.
For whatever reason, this can lead to many useful results becoming lost or disregarded.