Once a year for the last five years, Google releases something called the "Android Security & Privacy Year In Review" — essentially a look back at the past year and the overall state of security for Android as a whole.
This year's report covers a lot of ground, but one number that stands out the most is the increase in security patch downloads. In Q4 2018, Google reports a year-over-year growth of 84%. In other words, a lot more devices are getting necessary security patches to keep them safe and secure.
To reach that number, Google attributes the success to Android One, the Android Enterprise Recommended Program, and "new OEM agreements."
On a similar note, as of December 2018, more than 95% of all Pixel 3 and Pixel 3 XL handsets had a security update that was released within the last 90 days.
Elsewhere in the report, Google talks about PHAs — also known as Potentially Harmful Applications. This includes stuff like spyware, phishing apps, and trojans. In 2018, Google says that just 0.08% of devices that only used the Google Play Store for downloading applications were affected by these PHAs. In 2018 alone, Google blocked 1.6 billion attempted PHA installations
Compared to 2017 when 0.45% of Android devices had PHAs despite exclusively using the Play Store, that's an improvement of 20% YoY.
The entire report is around 30 pages long, so if you feel like diving into all of the nity gritty, feel free to give it a look.