How Much SETI Has Been Done?

The completeness of the search for signs of extraterrestrial radio transmissions and other technosignatures to date is roughly equivalent to having searched a small swimming pool for evidence of fish in all of Earth’s oceans.

How Much SETI Has Been Done? Finding Needles in the n-dimensional Cosmic Haystack
Jason T. WrightShubham Kanodia, and Emily Lubar 
The Astronomical Journal
Volume 156Number 6

Image credit: NRAO/AUI/NSF