The Verizon report is a great asset for getting an understand of what's going in the industry. They've been publishing the report for 15 years and it's a go-to for cyber and non-cyber leaders.
Their research shows that external attacks are the primary cause of data breaches, with three out of four cases pointing to sources outside the organization. Business partners were involved in 39% of these breaches. Internal sources accounted for only 18% of incidents, a four-to-one ratio compared to external origins. Contrary to popular belief, insider incidents were less frequent in cases of data compromise, although they are skilled at keeping their activities secret.
Access and read the entire report: https://www.verizon.com/business/resources/reports/dbir/