It’s very important to write a summary, but also you should be able to retrieve the historical data to understand the actual shift in performance. For this purpose, it’s very convenient to use Performance Management Tool where you can have data from every employee and have the ability to see the dynamic in employee's growth or detect concerning signals. For example, you can use a free Performance Management Tool like Effy provided with analytics, like skill set analysis, spider graph performance report and others. You can sign up for free and try it out.
