The review period of analysis should, where possible, be the most recent 12 months for which data is available. A longer or shorter or different period may however be appropriate in specific circumstances.
If you find a dimension intereseting, we recommend you pick up one or two facts that you find intriguing and place them into your memory. That way you will have 2nd degree information about the topic if it comes up in conversation.
Accordingly, you can do the same with others as well.