The Kepler mission using the transit method , IIRC, attempted to survey 150,000 stars.How many stars were studied that came up empty and surveyed before less than 4,000 stars can be shown with exoplanets, I do not know.
The article did mention that the no. of exoplanets is about equal to the no. of stars. This isn't something new, but a lot more data is needed to tweak this estimate.So my observation here. There are billions of stars in the MW, yet today we know < 3700 have exoplanets. The article title stated, "Does every star have planets?" My answer is no and the article is a easy to read and understand too.