Welcome to edition 308 of Insider Weekends. Insider buying increased last week with insiders buying $79 million of stock compared to $43.91 million in the week prior. Selling decreased with insiders selling $1.84 billion of stock last week compared to $2.43 billion in the week prior.

Sell/Buy Ratio: The insider Sell/Buy ratio is calculated by dividing the total insider sales in a given week by total insider purchases that week. The adjusted ratio for last week dropped down to 23.26. In other words, insiders sold more than 23 times as much stock as they purchased. The Sell/Buy ratio this week compares favorably with the prior week, when the ratio stood at 55.46. We are calculating an adjusted ratio by removing transactions by funds and companies and trying as best as possible only to retain information about insiders and 10% owners who are not funds or companies.

Note: As mentioned in the first post in this series, certain industries have their preferred metrics such as same store sales for retailers, funds from operations (FFO) for REITs and revenue per available room (RevPAR) for hotels that provide a better basis for comparison than simple valuation metrics. However metrics like Price/Earnings, Price/Sales and Enterprise Value/EBITDA included below should provide a good starting point for analyzing the majority of stocks.

Notable Insider Buys:

1. IDI, Inc. (IDI): $5.35

Shares of this data and analytical solutions provider were acquired by 2 insiders:

We were a little surprised to see this purchase by Dr. Frost as most of his large purchases in the past were related to the healthcare company Opko Health (OPK) where he serves as the Chairman and CEO. This is his largest purchases in IDI since we started tracking insider transactions back in 2010 and leaves him with a 34% stake in the company following the purchase.

Dr. Frost began his career in 1972, when he bought Key Pharmaceuticals along with Michael Jaharis and turned the company around. He was Chairman of the Board of Directors of Key Pharmaceuticals until 1986 when it was acquired by Schering-Plough for $587 million. After the acquisition of Key Pharmaceuticals, Dr. Frost founded the IVAX Corporation in 1986 along with Dr. Jane H. Hsiao, the current CTO of Opko Health.