In a victory for common sense, the trading behavior of company executives, directors, and large shareholders in the stocks of firms they're registered "insiders" at have been proven profitable to monitor by both academic studies and (more importantly) the experience of your fellow professional investors.

Below are lists of the top 10 mainly open-market insider purchases and sales filed at the Securities and Exchange Commission Friday, February 2, 2013 as ranked by dollar value.

Please note, however, that these are factual lists, not buy and sell recommendations. Dollar value is only one metric to assess the importance of an insider transaction, and, frankly, often not even the most important metric that determines if an insider transaction is significant.

In purchases, Young Innovations Holdings LLC bought $312,602,560 worth of Young Innovations (NASDAQ:YDNT), a developer, manufacturer, and marketer of dental supplies and equipment. Noubar Afeyan, a Director of BG Medicine (NASDAQ:BGMD), which specializes in cardiovascular diagnostics, bought $4,000,000 worth of the company stock. Afeyan is the CEO of the venture capital firm Flagship Ventures. Also at BG Medicine, Director Stelios Papadopoulos bought $500,000. Dr. Phillip Frost, the CEO and Chairman of pharmaceutical and diagnostics company Opko Health (NYSE:OPK), bought $258,000 worth of company stock. Constantine Karayannopoulos, the President and CEO of rare earth oxide mining company Molycorp (NYSE:MCP), bought $100,002 worth of company stock.

In sales, Daniel Loeb, a Director of Yahoo (NASDAQ:YHOO), sold $216,663,024 worth of company stock. Loeb is also the founder of the hedge fund Third Point LLC. At Google (NASDAQ:GOOG), Director Kavitark Shriram, one of the company's initial investors, sold $15,203,040. Roger Fradin, the President and CEO of diversified technology and manufacturing company Honeywell International (NYSE:HON), sold $3,422,000 of company stock. There were several sales at semiconductor company Texas Instruments (NASDAQ:TXN), with Senior Vice President of Technology and Manufacturing Kevin Ritchie selling $2,736,205, Senior Vice President of Embedded Processing Gregory Delagi selling $2,407,020, Senior Vice President and Manager of Worldwide Sales and Marketing John Szczsponik selling $1,915,379, and Senior Vice President and Manager of offshoot Silicon Valley Analog selling $1,532,330.

At InsiderInsights.com, we find new investment ideas just about every day using these and more intricate insider screens to determine where we should focus our subsequent fundamental and technical analysis. And while stocks don't (or shouldn't) move up or down based on insider activity alone, insiders tend to be good indicators of when real stock-moving events like earnings surprises, corporate actions, and new products may be in the offing.

Insider Purchases

#:	Filer Name	Insider Titles	Company Name	Ticker	Trans Type	Dollar Value
1	Young Innovations	BO	Young Innovations	YDNT	JB*	$312,602,560
2	Afeyan Noubar	DIR,BO	Bg Medicine	BGMD	JB*	$4,000,000
3	Orbimed Advisors	DIR	Anthera Pharm	ANTH	JB*	$3,762,000
4	Papadopoulos S	DIR	Bg Medicine	BGMD	JB*	$500,000
5	Frost Phillip MD	CEO,CB,BO	Opko Health	OPK	B	$258,400
6	Straus Asset Mgt	BO	Sunshine Heart	SSH	B	$257,739
7	Kondracke M	DIR	Bright Horizons	BFAM	JB*	$220,000
8	Karayannopoulos C	PR,CEO,DIR	Molycorp	MCP	JB*	$100,002
9	Simmons Harold C	CB,DIR,BO	Kronos Worldwide	KRO	B	$96,250
10	Tocio Mary Ann	PR,COO,DIR	Bright Horizons	BFAM	JB*	$88,000

Source: InsiderInsights.com | Key to Insider Title and Trans Type Codes
 

Insider Sales

#:	Filer Name	Insider Titles	Company Name	Ticker	Trans Type	Dollar Value
1	Loeb Daniel S	DIR	Yahoo	YHOO	S	$216,663,024
2	Shriram Kavitark R	DIR	Google	GOOG	AS	$15,203,040
3	Fradin Roger	PR,CEO	Honeywell Intl	HON	AS	$3,422,000
4	Credit Suisse Ag	BO	Walker & Dunlop	WD	AS	$3,164,292
5	Ritchie Kevin J	VP	Texas Instruments	TXN	AS	$2,736,205
6	Delagi R Gregory	VP	Texas Instruments	TXN	S	$2,407,020
7	Carroll Kenneth	BO	Diligent Board Svs	DIL.NZ	JS*	$2,163,385
8	Szczsponik John J	VP	Texas Instruments	TXN	AS	$1,915,379
9	Broadbent Peregrine	VP,CFO	Jefferies	JEF	S	$1,759,086
10	Heacock David K	VP	Texas Instruments	TXN	AS	$1,532,330

Source: InsiderInsights.com | Key to Insider Title and Trans Type Codes

Editor's note: Jonathan Moreland is the founder of Insider Insights and author of "Profit From Legal Insider Trading."