Summarize multiple columns in a chart

One way I have done this in the past is to do the calculation using a parent table with a master parent record. Essentially I set up a table so I can summarize the values across records up to it with a single Master Parent Record. Then you can go in and set all the existing records to be related to that 1 record. Build out a summary field for # of records with age great then 50, another summary field with # of records less then 30 and a final field to bring up total number of employees. This creates all of your summarized values in a single record, which means you can then do a calculation on the summarized values. Once the existing records are all related to the single existing Master Parent Record you can then set the related Master Parent Record field in the Employees table to default to 1 and all new records will automatically associate.