Hyperbolic headlines aside, the only people who tend to see issues or politicians being “eviscerated” by Last Week Tonight are ideologically liberal. If a conservative voter watched any of the show clips the above headlines reference, he or she likely wouldn’t see an evisceration, but rather an attack by a biased media. (And, to be fair, the aforementioned conservative also wouldn’t see an evisceration because it’s a near certainty he or she wouldn’t be watching the show in the first place.)

Look at Last Week Tonight’s ancestor, The Daily Show. Its viewers are more politically knowledgeable than most others. Further, its viewers also skew overwhelmingly liberal. Add in the fact that viewers of all ideologies tend to select media sources based on ideological leanings, and it becomes very difficult for any of these late-night segments—be they delivered by Oliver, Samantha Bee, or Trevor Noah—to reach anyone outside a predominantly liberal audience.

Thus, it’s not hard to imagine a scenario where the “interest” created by late-night comedy is merely amplification within an echo chamber. The segments appeal to a liberal audience who may already know about the issue—or are otherwise likely to agree with the show’s position regardless. This also likely explains why interest dies down immediately thereafter—the same audiences are merely moving on to the next segment to share within the same circles. Which, in turn, explains why late-night comedy rarely causes policy change—it undoes its own work the moment the next segment airs.

Last Week Tonight makes for a great case study, as each episode covers at least one story in substantive detail, devoting several minutes to it if not the entire show. In some cases, the top story is so widely covered in the news that it’s impossible to isolate amid the larger conversation around the topic online. Trump’s rise is a great example of this. But in other weeks, whether it’s because the news cycle is slow or because Oliver feels strongly enough about a particular issue, the top story is evergreen—or newsworthy regardless of timing. In those weeks, you can frequently see that Oliver’s show does cause an increase in interest around that subject. The web-analytics firm Parse.ly pooled its data to chart this “John Oliver Effect.” But interest isn’t the same thing as action, which itself is a far cry from political change.

As Parse.ly notes, Oliver’s impact is strongest when it comes to relatively unknown issues, and quickly weakens the more prevalent the issue is. Take, for example, Last Week Tonight’s investigation of daily fantasy sports. The segment aired on November 15, 2015. Per Google Trends, there was a modest uptick in interest the week before the segment, but it’s been in decline since the segment aired—and is much lower than its peak several weeks before the segment.

The show’s investigation of paid parental leave, which aired on May 10, 2015, is a good example of its ability to generate temporary interest. There’s a notable uptick in interest in the topic immediately after the segment aired; it’s not a huge logical leap to say the segment caused the interest. But a week after the segment, interest fell back to previous levels.

To be fair, conflating temporary interest with change is an easy trap to fall into. It’s true (and compelling) that the FCC website crashed immediately after Oliver’s segment on net neutrality, but examining the glut of comments that crashed the site reveals that relatively few are explicitly tied to Oliver or Last Week Tonight. Similarly, Oliver’s “Our Lady of Perpetual Exemption” church, established to complement his piece on televangelism, received a staggering amount of donations—enough that Oliver closed it rather quickly and donated the proceeds to Doctors Without Borders. Yet televangelism hasn’t gone anywhere, and while the donation is certainly a net positive, it’s a small blip on the radar that didn’t translate to long-term results.