As of June 2020, there were 3,569,305 FERS participants in the Thrift Savings Plan.
However, only 666,175 people actually had money in the Roth TSP— only about 18% of all folks enrolled in the plan! Additionally, the average Roth balance for the FERS population was a paltry $15,740 compared to an average balance of $146,801 for the Traditional TSP.