There are many, many institutions preforming global IPv4 scans daily and many tools that allow you to do it[0][1][2]. The trick is to "Be a good citizen", work with a scan friendly host, signal your benevolence, and limit the rate at which you scan. Also smart to black-list DoD networks. If you don't believe me setup a honey pot and open up a popular udp amplification port. Haven't done so myself but I would expect many instances of scanning would be seen everyday.

[0]:https://zmap.io/ [1]:https://github.com/robertdavidgraham/masscan [2]:https://memcachedscan.shadowserver.org/