This pattern sets up a hypothetical situation or assumption, often leading to a conclusion or consequence. It is a conditional form similar to たら or ば, but it explicitly frames the condition as an 'if we suppose' or 'given that' scenario. It can be used with facts that may or may not be true, and the speaker often implies some doubt or formality.

You will hear it in discussions, formal speech, and writing. In conversation, you might prefer the simpler たら or ば, but とすれば adds a nuance of 'if we take it as so'. The construction is と (quotative particle) + すれば (conditional of する), so it literally means 'if (one) says'. It is standard in both spoken and written Japanese, though it sounds a bit bookish in casual chat.