As a conjunction, that is often optional. But when two or more corresponding phrases are involved, employ it consistently or omit it altogether, as explained in the discussion and shown in the revision following each of these examples.
1. It is healthy to recognize that biases exist and everyone has them.
In this sentence, “everyone has them” might be read as an afterthought rather than a second consideration parallel with “biases exist.” To strengthen its correspondence with the earlier phrase, repeat that: “It is healthy to recognize that biases exist and that everyone has them.” (A misreading is unlikely to occur if the sole instance of that in the original sentence is deleted, but the sentence is more effectively rendered with that inserted before each phrase.)
2. More than three out of four respondents indicated their organizations are either facing strong pressure to reduce costs or that they are facing increased demand to manage spending levels.
Here, if the sentence ended with costs (with either no longer necessary), inserting that after indicated would be discretionary. But if the writer uses it after the conjunction or, it must also appear in the corresponding position in the first part of the sentence, and either must be shifted to an earlier position: “More than three out of four respondents indicated either that their organizations are facing strong pressure to reduce costs or that they are facing increased demand to manage spending levels.” Alternatively, it can be deleted after or as well, in which case either must remain in its original location. (However, consider a third option that renders an earlier instance of that unnecessary and simplifies the sentence: “More than three out of four respondents indicated that their organizations are facing either strong pressure to reduce costs or increased demand to manage spending levels.”)
3. Get the facts out and make sure all sides of the issue are voiced, all relevant facts are obtained, and that everyone whose opinion is valued is heard.
In this case, because of the list structure, that need not be repeated for each list item, but if it is to be employed at all, it must be inserted at the head of the list: “Get the facts out and make sure that all sides of the issue are voiced, all relevant facts are obtained, and everyone whose opinion is valued is heard.”
