Brokers vs. Brokers in the Closing Auction

The Xetra Flows Insights show the net volume (bought - sold) for a number of categories (aggressive vs. passive, continuous trading vs. auctions, buy vs. sell) split by participant subset: customer (agency), and non-customer (market makers and proprietary). But it also includes the gross volumes for each bucket. This allows one to get a sense of the market shares of each participant group during continuous trading and the auctions.

Fig. 1 below shows the time series of the "customer" market shares (non-customer constitutes the remainder to 100%).

Note the change during 2019. This doe not reflect a change in actual composition of the trading participant or their strategies. Instead it is caused by a stricter interpretation and enforcement of the correct account type designation.

Interestingly, the "customer" market shares are almost the same for aggressive and passive trades - if anything it is higher for the passive trades. I would have expected the presence of market makers to lower the passive customer market share.

The auctions are dominated by brokers. There is very little market maker or proprietary flow in the auctions. But while the daily aggressive and passive market shares are within a narrow band, the customer market share in the auctions has a much higher variance.

BTW: The chart shows data aggregated over all DAX constituents. The actual dataset includes stock-by-stock data and not just for the DAX40. There is also a separate dataset for ETFs.