As Mark Twain once noted, there are three types of lies: Lies, Damn Lies, and Statistics.
For example, it is well known that Russia is the most likely country to be struck by a meteorite.. and the rate was much higher under the Soviet Union. Clearly there is a God and he's American!
Of course, once you realize that Russia is the largest country by landmass in the world, and the Soviet Union was bigger because Russia was one of a handful of nations within the Soviet Union, it has nothing to do with Russia and everything to do with with being a large country. If a meteor is going to hit earth, the most likely impact zone is somewhere in the ocean because 75% of Earth is ocean. But if it's going to strike a country, it's most likely to hit Russia because Russia is bigger than any other country.
Another fun one, it is a well known fact that in the United States, ice cream sales and violent youth crime increase and decrease at identical rates during identical observation times. Natrually we must ban Ice Cream, which is corrupting our youth! THINK OF THE CHILDREN!
Of course, what's omitted is that an increase in ice cream sales and an increase in youth crime at similar rates would normally be observed in Late Spring to Summer, while the decrease would occur in late fall and winter... because Ice Cream is typically sold in summer months to beat the heat, which also is when school is out, which leads to kids having more free time to do things kids do... including Youth Crimes. Don't give up your 31 flavors for just that.
Another thing to look at, when citing sources related to nations, is to look at sample size, rather than total numbers. Take a look at the leader boards on this Wikipedia Page for Nations by Gun Homicide. First it's important to note that all figures are sampled at a a per capita rate of 100,000 citizens, so that each country can be comparable in rates of incidents EXCEPT for the total available guns per capita, which is for 100 people. I'll be putting that stat into 100,000 for convenience so that I can sub Per Capita for 100,000 population (also cause the page does not clearly show this.). It should also be noted that the total guns available assumes all weapons, legally owned or otherwise.
If we look at this page, we can see that the United States clearly leads the pack in gun ownership at a rate of 112,600 guns per capita and is the only nation with more guns than people on this chart! In total numbers, 12,999 individuals died in gun related homicide (The 14th highest world wide). The Gun Homicide Rate in the United States is 4.2 deaths per capita (The 88th highest world wide). So how can this be?
Well, we're measuring several different statics. First, gun ownership rates have little to do with gun homicide rates or total homicides. For example, by total numbers alone, the top three Leaders are Brazil (40,974), India (~40,752), and Mexico (~25,757) and have respected 8,000, 4,200, and 15,000 guns per capita. The gun homicide rates are also surprising as there is a respected, 21.0 per capita, 3.4 per capita, and 16.9 per capita. India, despite having nearly 4 times as many total gun homicides than the United States is lower in it's incident rate than The United States and Mexico, but all three of those pail in comparison to Brazil's rate, which isn't the highest rate in the world (Houndoras, at 91.6 has the highest rate).
Like the Russia trick, size matters. India is second largest nation in the world by population and one of only 2 nations with over a billion people. The United States is a distant Third, with about 320 million people. Brazil is sixth with 210 million people. Mexico is 11th with 123 million people. Per Capita statics are measured by dividing the total number by the total population and than multiplying by 100,000 (or what ever your per capita rate is. There's no rule that says it has to be 100,000, but these stats are usually given in per 100,000 members of population). Thus, 40,000 divided by 210 million is a much larger number than 40,000 divided by 1 billion people, while 25,000 into 123 million and all are larger than 13,000 into 320 million (Cause that's how fractions work). But these numbers are big because like Russia's "Mo' land, Mo' Metorites" problems, these nations operate under "Mo' People, Mo Problems". If you had to pick a country anywhere in the world that would likely to have a gun homicide, you'd go for the ones with larger populations because there is a greater chance to have someone who will kill another person in that country.
And because I got into a debate with some British people about how you need a Per Capita rate when comparing countries with various populations sizes, I can say with confidence that U.S. Medicare and Medicade cover more people than the UK's Universal Health Care plan. This is because the two programs cover 120 million people combined, which is double the entire population of the United Kingdom (~60 million). With Per Capita standardization, we're treating all stats without discrepancy of the population. Thus, the question of "Who's Health Care system is better?" doesn't rely on the United States being more than 5 times the population size of the U.K. but which is better to have? 287 million people out of a total 320 million covered OR 60 million out of 60 million people covered? If we are going by sheer bulk, than the United States wins in a landslide. If we're talking in percentage of population, than the U.K. is the winner.
I throw these numbers up not to pick a side, of any debate (except that, in summer, I scream for Ice Cream and I scream for solutions to kids graffiti my house, but that doesn't mean the later is caused by the consumption of the former). I merely selected them to show that anyone can take the numbers and torture them enough to say something that supports them.
With respect to the gender pay gap, the statistic (I think it's 78% of what a man makes, not 80% but that's a quibble at best), the figure was taken by finding the average salary of men and the average salary of women and divided tha latter by the former. Yes, that pay gap exists... but it does not indicate that a woman and a man doing the same identical job, for the same amount of time and same quality of work will see a difference in pay, which leads to debates about the gender pay gap. It is correct to say that in the United States, the average salary for woman is 80% of the Average salary for men. It is also correct to state that women in the work place have faced behaviors from men that are inappropriate. It is also correct that some of these inappropriate behaviors have been reduced pay for women. It is incorrect to say that this 20% difference in pay is solely attributed to malicious actions by men (it contributes but isn't the only factor). Just like it is correct to say that Ice Cream Sales and Youth Crime both experience peaks and troughs at the same periods of time, it is incorrect to say that more Ice Cream corrupts the kiddies or that youth offenders favor ice cream over any other snack... there could be some cross over. I'm sure Ice Cream does rate high if you want to know what Youth Offenders like to snack on and some youth offenders may try to steal ice cream from stores, but the connection between Ice Cream and Youth offenders are not co-dependent.
Another example is the (in)famous book Seduction of the Innocent which suggested that Comic Books were corrupting children and killed the Golden Age period of Comic Books and damn near the entire industry... during this time, Superheroes weren't the only genre... there was also horror, fantasy, tales of Soap Opera styled lives... but these were written for adults and teens, not children. The two most damning accusations in the book was that Batman and Robin promoted a homosexual lifestyle and Wonder Woman had sexual subtext promoting Lesbianism. In the Batman and Robin charge, this was uncovered by the author interviewing boys who were institutionalized for Homosexuality and learning that they liked to read Batman and Robin and identified with Robin. It failed to take into account that Robin was meant to be a character for the young male audience to identify with and damn near every superhero had a childhood sidekick during this time. If he were to ask Straight kids who their favorite Batman character was, they probably would answer with Robin too. In the case of Wonder Woman, its a case of "right for the wrong reason". Wonder Woman was contracted to a professor to write and tasked him to write a "Superman for Girls" character. Unknown at the time, the professor was a polygamist and into bondage... he also invented the polygraph. And now you know why Wonder Woman's signature weapon is a Lasso of Truth. It also explained why Wonder Woman's early comics involved tying up other women or herself being weakened when bound. Like in the case of Robin, gay girls enjoyed reading Wonder Woman because she was written as a superhero that young girls would enjoy reading about. Straight girls probably liked the stories just as much as gay girls.
And like all of these statisitics, when accounting for other factors, such as equal pay in the same job/job field (i.e. pay differences between men and women in computer programing or teaching) and hours worked, quality of work, and all other factors, there is still a gap favoring men, but that gap is reduced to 1-2% difference. $0.98 for ever $1 a male makes. In statistics, this is an insignificant difference that falls within margin of error and can be attributed to factors not controlled for, possibly misogyny in the system, or possibly over or under reporting or other data entries. There could be a relationship, there could not be. More study required. The reason the greater gap is touted though is to bring attention to an issue. It's a popular talking point and some people use it knowing that society disadvantages are not the root cause, but the assumption that is what is happening is the root cause and others use it because they got the stat from somewhere citing it.
Or as Homer Simpson, who's intelligence is legendary, once noted, "Anyone can make up a statistic. 40% of all people know that!"