169. Corporate officers and directors commonly buy and sell, for their own portfolios, stock in their own corporations. Generally, when the ratio of such inside sales to inside purchases falls below 2 to 1 for a given stock, a rise in stock prices is imminent. In recent days, while the price of MEGA Corporation stock has been falling, the corporation's officers and directors have bought up to nine times as much of it as they have sold. highlight这句话什么意思？谢谢！

169. Corporate officers and directors commonly buy and sell, for their own portfolios投资组合, stock in their own corporations. Generally, when the ratio of such inside sales to inside purchases falls below 2 to 1 for a given stock, a rise in stock prices is imminent. In recent days, while the price of MEGA Corporation stock has been falling, the corporation's officers and directors have bought up to nine times as much of it as they have sold.

可不可以拜求整段中文解释  
inside sales to inside purchases  是只助理类的职称还是另有其他解释

请教一下，原题说，Generally, when the ratio of such inside sales to inside purchases falls below 2/1...., the stock price will rise

Generally,能代表普遍的状况吗？题干中来个转折，while...我就以为发生的是一种和generally不同的状况

有NN能帮忙分析一下吗？