What is the advantage in using the written record over other methods when it comes to reactivity?

What will be an ideal response?

Data from archival sources are usually nonreactive. Human subjects often consciously or unconsciously establish expectations or other relationships with investigators, which can influence their behavior in ways that might confound the results of a study. But those writing and preserving the records are frequently unaware of any future research goal or hypothesis or, for that matter, that the fruits of their labors will be used for research purposes at all. Record keeping is not always completely nonreactive, however. Record keepers are less likely to create and preserve records that are embarrassing to them, their friends, or their bosses; that reveal illegal or immoral actions; or that disclose stupidity, greed, or other unappealing attributes. Furthermore, many record-keeping agencies employ paper shredders to ensure that a portion of the written record does not endure. Researchers must be aware of the possibility that the written record has been selectively preserved to serve the record keepers’ own interests.