A cross-measurement system gathers data from a set of publishers to determine cross-publisher statistics about content provided on multiple online platforms associated with different publishers. The cross-measurement system receives a set of publisher-specific Bloom filters associated with content exposure of a content set by each of the multiple publishers. using the received publisher-specific Bloom filters, the cross-measurement system generates a cross-publisher Bloom filter, for example, by combining the publisher-specific Bloom filters. Then, the cross-measurement system analyzes the cross-publisher Bloom filter to determine cross-publisher statistics reflecting the content exposure of the content set across the set of publishers, such as a cross-publisher reach of the content set.