from what I can see only these activities are available...
items
| name | uri | created By | created At | updated By | updated At |
|---|---|---|---|---|---|
| Registered | /activities/types/1000 | BaseInstall | 2009-10-25T16:01:57.4330000Z | BaseInstall | 2009-10-25T16:01:57.4330000Z |
| Attended | /activities/types/1001 | BaseInstall | 2009-10-25T16:01:57.4330000Z | BaseInstall | 2009-10-25T16:01:57.4330000Z |
| Visited Booth | /activities/types/1002 | BaseInstall | 2009-10-25T16:01:57.4370000Z | BaseInstall | 2009-10-25T16:01:57.4370000Z |
| Viewed a Demo | /activities/types/1003 | BaseInstall | 2009-10-25T16:01:57.4370000Z | BaseInstall | 2009-10-25T16:01:57.4370000Z |
nothing here seems helpful with regard to open rate data