Why does changehistory take so much space now?

Question

Upon migrating from ARS 6.9 to 7.1 I noticed that the change history database quadrupled in size after importing the previous version's change history database. Is this typical?

Aidar.Karabalaev · Answer

Assume you got CH 7.1 for 1year and imported CH6.9 for another 1year (same length). 
Speculations of different sizing: 
(a) CH 6.9 can contain legacy bulk updates (QC, scheduled scripts) changes. in 7.1 the legacy workflows was decommissioned due AD management workflow changes in general. 
(b) V6.x used to have issue: Group Memebrship changes used to be recorded ALL members Old and New value for member attribute. In 7.1 the issue was resooved, and the only added/removed member is recorded in CH.