Citadel Securities pulled in roughly $7.3 billion in trading revenue during the second quarter, a figure that makes its already strong Q1 look modest by comparison. The electronic market maker, founded by billionaire Ken Griffin, posted about $4.3 billion in the first three months of the year.

The Q2 number represents the firm’s best quarter on record, driven by surging retail investor activity and all-time highs in both US equity and options trading volumes.

What’s behind the numbers

Citadel Securities has historically commanded roughly 25% of all US equity trading volume, making it one of the largest market makers on the planet. Its business model is relatively straightforward in concept: sit between buyers and sellers, capture the bid-ask spread, and do it billions of times across millions of securities.

Cash equity volumes in May reportedly exceeded prior peaks by more than 10%, while options premium trading hit new highs in June. The Q1 figure of $4.3 billion already represented a 27% increase year-over-year.