Pokemon GO: What does throwing a Curveball do?

In Pokemon GO it takes a good amount of practice, but throwing a good Curveball will add up benefit-wise if done consistently.

While the XP bonus for throwing Curveballs is well known, the mechanics of the throws themselves are somewhat debated among Pokemon GO's faithful. Do the throws improve catch chances? Does the accuracy in the aiming ring help? Thanks to the dedicated work of The Silph Road, players have confirmation that Curveballs do indeed assist in catching Pokemon even without an accuracy bonus.

Pokemon GO's studied community members have even provided graphics to further illustrate their testing.

Pokemon GO: Curveballs by the numbers

To figure out just how Curveballs benefit Pokemon GO players in their catch encounters, The Silph Road has tested thousands of Pokemon encounters accounting for things like accuracy and CP total. However, they did implement a number of control factors in order to accurately record their data without outside factors interfering. Specifically:

Pokemon samples studied were collected before the Type Catch Bonus implementation from Niantic went live. The Type Catch Bonus improves catch rate towards Pokemon of a certain type based on how many a trainer has cumulatively caught in Pokemon GO. These can be tracked by the medals attained on the trainer's profile tab.
The only Pokeballs used were the base Pokeballs. Since Great and Ultra Balls offer a significant increase in catch rate, this is a no-brainer.
The study excluded Pokemon attracted via Incense and Lure Modules.
The only Pokemon used in the study were those with the same base catch rate. At the time of the study, these included Rattata, Pidgey, etc.
Percentage of maximum CP was used in order to correlate a Pokemon's approximate level.

Based on their results, The Silph Road found that when landed as a Nice or Great Throw, Curveballs did improve catch chances over normal throws. This additionally applied to throws that received no accuracy bonus from landing within the aiming ring. The samples for Excellent Throws were inconclusive, but it can be assumed that Niantic would apply the Curveball bonus to those throws as well, as every other category was complemented by it.

Below are the charted results for straight normal throws. The colors emphasize the percentage of a Pokemon's maximum CP. The left axis represents the percentage of samples that were caught successfully.

While by contrast, this chart shows the same with regards to Curveball Throws:

With this information, Pokemon GO players may want to put in a little practice hitting their ideal Curveball Throws. For those tough-to-catch Pokemon, the bonus from the throw very well may make all the difference in catching the Pokemon or watching it flee.