Six billion people clinging to this spinning blue marble, each with unique fingerprints and breakfast preferences, but make a public declaration of your chosen profession and brace for instant, universal judgment. You’re a doctor? they ask, the words loaded with assumption. Or: You sell used Hyundai’s? And there are those assumptions again—though this time considerably less generous.

A slew of studies have been conducted over the years that lend authority to the associations people, armed with occupational information alone, will make about you.

One of them, conducted some time ago by an American publication called Work, named firefighting as the world’s most honest calling. Last year, a poll by Reader’s Digest China magazine came to the same conclusion.

In 2004, a Gallup survey of the most honest professions picked nurses, teachers and pharmacists for the top three spots, and relegated lawyers, advertising practitioners and car salesman to the lowest ranks of the scale.

In 2007, a Sympatico/MSN survey also tapped firefighters as the most trustworthy in the country (93%), followed by nurses (87%) and pharmacists (86%). Among the least trusted professions? CEOs (ugh…must I change my profession?), trade unionists, politicians and automobile floggers.

More recently, a 2011 survey from market research firm Ipsos Reid called pharmacists the world’s most trusted professionals, with a 79% rating. Doctors and airline pilots ranked a close second (both clocking 75%) and Canadian soldiers scored third (72%).

At the opposite end of the list, find car salespeople (just 8% of us gave these characters high marks for credibility), national politicians (9%) and union leaders (17%).

The results reveal an interesting departure, in some cases, from those released in a similar survey eight years ago. Canadians’ faith in police officers, for one, has declined meaningfully, with 73% of Canadians saying cops deserve the highest points for trustworthiness in 2003, and just 57% making the same claim today.

Teachers’ reputations took a vicious slide, too, down 14 points to 65%. Pharmacists dropped 12 points, doctors fell 10, new home builders slumped eight, and auto mechanics, declared trustworthy by 25% of today’s survey participants, were considered reliable by 33% of us in 2003.

Our confidence in other professions, meanwhile, has shot up. At 72%, significantly more Canadians trust our nation’s soldiers today than in 2003 (up 15 points). And chiropractors, whose 44% trust quotient is four points higher than in 2003, are perhaps benefitting from the pain in the neck our municipal politicians collectively inflict.

Speaking of whom, even though just 17% of us cop to trusting our locally elected officials, that’s up three points from the last time anyone asked. On the Work survey, local politicos scored even lower on the honesty scale, coming in just five positions above drug dealers, and two above prostitutes.

Overall, it’s meaningful to note that we basically appear to trust everyone less. Even the number-one rated profession for credibility, pharmacist, ranks 12% lower than it did in 2003. Of the top four (pharmacists, doctors, airline pilots, soldiers and teachers), just one—soldiers—experienced an increase, spiking 15% since 2003.

And so the assumptions endure. You say you’re a plumber? Surely you’re bending our pipes (trustworthiness: 39%, down 3%). A journalist? We don’t believe your stories (29%, down 2%). A lawyer? You’re courting a serious lack of faith (22%, down 7%). And on.

Your best bet? Survey conductor. We seem to believe these guys.