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To avoid confusion, use a comma after an introductory subordinate clause or phrase:

  • Because the costs of conducting research continue to increase, we need to raise our rates.
  • As the shrimp boats trawl, sea grass can collect on the trap door, allowing shrimp to escape.
  • According to the professor, rich women are more likely to have Cesarean sections than poor women.

In keeping with the modern trend toward using as little punctuation as possible, some stylists believe that it is not necessary to place a comma after short introductory words (now, thus, hence) and phrases (In 1982 he committed the same crime). However, conservative style manuals still call for the comma, so you are better off playing it safe and placing a comma after introductory words and clauses.

Other comma resources: