Complex sentence: This year is the 25th anniversary of the Mavis Beacon Teaches Typing retail software product and since the introduction, Mavis Beacon Teaches Typing has been the best selling typing software (according to NPD Group data).
Split into simpler sentences: This year is the 25th anniversary of the Mavis Beacon Teaches Typing retail software product. Since its introduction, Mavis Beacon Teaches Typing has been the best-selling typing software (according to NPD Group data).