# Just how effective are background checks? **URL:** \ **Category:** Great Debates\ **Created:** [November 17, 2016, 3:33pm UTC](https://boards.straightdope.com/t/just-how-effective-are-background-checks/772260 "2016-11-17T15:33:39Z")\ **Posts on this page:** 1\ **Showing post:** 14
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [November 19, 2016, 9:17am UTC](https://boards.straightdope.com/t/just-how-effective-are-background-checks/772260/14 "2016-11-19T09:17:38Z")
> [@Sage\_Rat](#): > > I used regression analysis to develop a Java application where you can play around with various statistics and see how it affects the homicide rate. […] I wanted to wait until there wasn’t just a big shooting that happened to post the application. I’ll do so tonight when I get home. Spoilering since this is an executable. You’ll just need to trust that it’s virus-free, I guess, but it was developed by me and has been modified by no other. Since it’s a Java jar, you might have to look on the web to see how to run it, though. It might not run straight off the bat, depending on how your system is set up. [Dropbox](https://www.dropbox.com/s/a9jcc4a5ap0o66q/homicide.jar?dl=0) It starts out with the USA dialed in. The stats on which the polynomial regression was run are: > **[List of countries by intentional homicide rate](https://en.wikipedia.org/wiki/List_of_countries_by_intentional_homicide_rate)** > > The list of countries by UNODC homicide rate is typically expressed in units of deaths per 100,000 individuals per year. A homicide rate of 30 (out of 100,000) corresponds to 0.03% of the population dying by homicide. The reliability of underlying national murder rate data may vary. Only UNODC-vetted data is used in the main table below. In some cases, it may not be as up to date as other sources. See further down as to why its data is used over other sources. > Homicide rates may be under-report... > **[Estimated number of civilian guns per capita by country](https://en.wikipedia.org/wiki/Estimated_number_of_guns_per_capita_by_country)** > > This is a list of countries by estimated number of privately owned guns per 100 people. The Small Arms Survey 2017 provides estimates of the total number of civilian-owned guns in a country. It then calculates the number per 100 people. This number for a country does not indicate the percentage of the population that owns guns. This is because individuals can own more than one gun. > See also: Percent of households with guns by country. It gives the percent of households with guns. It is furthe... [http://hdr.undp.org/en/composite/GII](http://hdr.undp.org/en/composite/GII) > **[List of countries by income equality](https://en.wikipedia.org/wiki/List_of_countries_by_income_equality)** > > This is a list of countries or dependencies by income inequality metrics, including Gini coefficients. The Gini coefficient is a number between 0 and 1, where 0 corresponds with perfect equality (where everyone has the same income) and 1 corresponds with perfect inequality (where one person has all the income—and everyone else has no income). > Income distribution can vary greatly from wealth distribution in a country (see List of countries by wealth inequality). Income from black market economi... > **[List of countries by ethnic and cultural diversity level](https://en.wikipedia.org/wiki/List_of_countries_ranked_by_ethnic_and_cultural_diversity_level)** > > This is a list of countries by ethnic and cultural diversity level, as per Fearon's analysis. > The lists are commonly used in economics literature to compare the levels of ethnic, cultural, linguistic and religious fractionalization in different countries. > Fractionalization is the probability that two individuals drawn randomly from the country's groups are not from the same group (ethnic, religious, or whatever the criterion is). In Fearon's analysis, only groups containing over one percent ... > **[List of sovereign states by sex ratio](https://en.wikipedia.org/wiki/List_of_countries_by_sex_ratio)** > > The human sex ratio is the comparative number of males with respect to each female in a population. This is a list of sex ratios by country or region. > The table's data is from The World Factbook unless noted otherwise. It shows the male to female sex ratio by the Central Intelligence Agency of the United States. If there is a discrepancy between The World Factbook and a country's census data, the latter may be used instead. > A ratio above 1, for example 1.1, means there are more males than fe... For the gender ratio, I subtracted 1 from the value since it doesn’t add anything. Some things to note: 1. The formula will pick a best-fit curve regardless of whether there was actually any real correlation. 2. Everything is a curve, since it’s based on polynomials. This performed better (i.e., the average difference between prediction and reality is closer) than linear regression, but that doesn’t mean that everything curves all nice like it does. A flat, horizontal correlation will end up as a bump or a dip, no matter what. (See point 1). 3. I remember noticing, back when I developed this, that Colombia was predicted to have a far lower homicide rate than given in the original data. However, I then later saw in a different set of data - for a different year - that the homicide rate in Colombia was basically what had been predicted. I’m not sure if the year that is listed on the Wikipedia was a bad year there (gang killings?), but it does seem plausible that countries on the edge of a metric are more likely to fluctuate wildly, so you might take that into account if you try dialing in different countries. So overall, this is possibly indicative of general ideas, probably not very good for real predictions, but also not horrible. It’s cold, reliable, math, but it’s not magic. --- _[View the full topic](https://boards.straightdope.com/t/just-how-effective-are-background-checks/772260)._