Incoming SMTP in the year 2017 and absence of DKIM

[Eric Kuhnke <eric.kuhnke () gmail com>]

For those who operate public facing SMTPd that receive a large volume of
incoming traffic, and accordingly, a lot of spam...

How much weight do you put on an incoming message, in terms of adding
additional score towards a possible value of spam, for total absence of
DKIM signature?