Kiplinger Personal Finance Magazine

Question: what percentage of overal trading volume are Personal Finance traders?
For example, how much are prices of stocks affected by institutions (e.g. funds) and how much by small personal traders. If they recommend a stock in a financial magazine (e.g., Kiplinger), will it affect its price significantly - individual traders wanting to buy it? How big volumes are "day traders" - 10%, 20% or 0.2%?
Answer: Goldberg and Lupercio, two analysts of the online trading industry, estimated that about 40% of all trading volume comes from a group of 50,000 "semi-professional" traders who use the major online brokerage firms. The analysis was for the year 2003.
So a good guess would be 40%.
Auburn University Women's Philanthropy Board 2010 - Knight Kiplinger