Group 1 - The article introduces the concept of bond index funds and highlights that many investors are familiar with stock index funds but not with bond index funds [2] - A free course is offered to educate investors on how to invest in bond index funds, including course notes and mind maps for efficient learning [2] Group 2 - The article discusses the "dulling effect" that occurs when the amount invested in a single investment is less than 5% of the total market value of the held funds, indicating that new investments have a minimal impact on overall performance [5][7] - It is noted that the dulling effect typically begins to manifest after 20 months of consistent investment with the same amount [7] - Two methods are suggested to address the dulling effect, one of which is the "regular but variable amount" investment strategy, where the investment amount increases as the market declines [8][9]