とされている・
とされている presents a classification, rule, status, or view as generally accepted. と考えられている presents an explanation or judgment as a view that people in the relevant community continue to hold.
Choosing between the two forms
Use とされている when the focus is an accepted classification, official treatment, rule, or status. Use と考えられている when the focus is an explanation, cause, or reasoned judgment. Both avoid presenting the statement as one particular person's opinion.
Classification and explanation
Notice the retained だ in the noun statement in the first example.
この施設の規定では、十八歳未満は子どもだとされている。
Under this facility's rules, anyone under eighteen is classified as a child.
AnalyzeThis reports an institutional classification rather than anyone's personal opinion.
この報告書では、湖の水質が変化した原因は周辺の土地利用にあると考えられている。
According to this report, changes in land use around the lake are considered the cause of the change in its water quality.
AnalyzeHere the reported content is a continuing explanation of a cause.
Why the final form matters
The final ている presents the view as currently established or still held. It is not simply describing one past act in which someone classified or considered something.
An established view or a conclusion now?
と考えられている emphasizes a view that is already held and remains in circulation. By contrast, と考えられる can present a conclusion that the writer regards as reasonably inferable at that point, even if it is not yet an established view.
More examples
この大会では、開始時刻を過ぎて到着した参加者は棄権したものとされている。
Under this tournament's rules, participants who arrive after the starting time are deemed to have withdrawn.
Analyze社内では、この手続きは安全確認の一部だとされている。
Within the company, this procedure is classified as part of the safety check.
Analyzeこの資料では、その記号は旧市街の境界を示すものとされている。
In this document, that symbol is considered to indicate the boundary of the old city.
Analyze業界では、この方法が標準だとされている。
This method is regarded as the industry standard.
Analyzeこの研究では、二つの変化は同じ原因から生じると考えられている。
In this study, the two changes are thought to arise from the same cause.
Analyze委員会では、新制度の導入が待ち時間の短縮につながると考えられている。
The committee believes that introducing the new system will lead to shorter waiting times.
Analyzeこの素材は、高温でも変形しにくいと考えられている。
This material is thought to resist deformation even at high temperatures.
Analyze