For me it's more business-like than that: am I more productive? There's also an element of (occasional) reader feedback and the increasing size of the audience and positive reaction to the materials. These things do not measure quality with any finesse, but do at least provide a crude indication of whether the perceived quality is above or below audience-acceptable levels.

Would you be okay with providing more context ? What kind of articles are you summarizing and for how long have you been doing it ? Have you read Shop Class as Soulcraft: An Inquiry Into the Value of Work from Crawford ? Any opinion on his description of a content farm ?

Are you reading literature ? Any changes in your reading pattern ?