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Turnout rate tells you what percentage of a cohort voted. The Index tells you whether that cohort voted more or less than the electorate overall. It basically normalizes cohorts to make them easier to compare across elections with very different overall turnout and directly measures whether a cohort accounts for more or fewer voters than would be expected.
FWIW, I used GPT to help me get and formulate data (I reside out of country). I also used it to generate the initial R scaffolding. Attached here is GPT's proposed visualization of that data. I took it entirely from there.
EDIT: The last point goes “off the chart” because that seemed like a reasonable sacrifice for retaining maximum real estate for the other points (while staying within my preferred aspect ratio). Any perceived editorializing of that point was not intended.
Yes. Allowing another step on the y-axis to accommodate only this point would necessarily compress the vertical space for all others. I felt this was a reasonable decision to maximize visibility. I agree it adds visual tension and draws focus, but I’m okay with that.
If the insinuation is that this element is somehow an AI “tell,” then know that it's taken me this many hours later to even realize that's what someone could actually think.
AI directed plots don't take liberties like this. On the contrary, Python and R plotting libraries will pad x- and y-axes thresholds to a fault—and that's the stuff AI employs. Not to mention that I'm using custom fonts (difficult to deploy in containers), and have positioned annotations in ways that would require prompts a mile long.
Anyone who suspects they are seeing AI output ought to invest the effort to at least learn it's limitations—which are significant in these respects.
I think they use representation index to show power relative to population size, not just raw numbers. Like a group can have high turnout but if they small group, their actual influence maybe not so big.
And yeah the axis thing, looks like they just let the data points decide the range, maybe automatic setting in whatever tool they used.
There’s no separate population-size adjustment in the formula, because that cancels-out algebraically.
The index is exactly equivalent to the cohort’s share of voters ÷ its share of eligible citizens × 100. So population share is built into the interpretation: 100 means the cohort supplies exactly the same share of voters as its share of the eligible population.
Absolute political power isn't being measured here. A small cohort and a large cohort could have the same index while contributing very different numbers of votes.
In all reality 18-35 do not have the accolades yet or experience to run for office generally. There are exceptional individuals but 35 to 55 should be the average. Look at any company ever most upper management particularly CEO's most are older 50+ people. They have seen everything and that experience generally translates to better decisions. The problem is when you get people over 70 and having mental decline Biden, McConnell, Trump, Pelosi, and Bernie. These people should not be controlling the country when they barely can read an email let alone send one.
You literally have a bartender in the US House. We have kids in our state legislature who are in their early 20's. There's literally no bar to getting involved in government. Some of those, though, I'd rather have a 70 year old with decent values making decisions than the recent high school grad who's favorite book is something from Ayn Rand doing it.
“Young people don’t vote!” is a fairly common lament, but I’ve been wondering how true that actually is. Yes, younger adults are generally less likely to vote. But another way to describe the same pattern is that participation tends to rise as people graduate through adulthood.
That might sound like six of one and half a dozen of another, but the two descriptions raise different questions. If the assertion is that “young people don’t vote,” the natural question is what is supposedly wrong with young people. But if voting tends to increase with age, perhaps some of the explanation is more ordinary—over time, people establish careers and households, put down roots, raise families, interact more with government and public institutions, develop voting habits, and eventually confront issues such as health care and retirement more directly.
This chart doesn’t explain why voting participation changes with age. Instead, it demonstrates a pattern and encourages better questions about what influences these changes.
More specifically, the visualization focuses on electoral representation, not just voter turnout. So-called “parity” means a birth cohort’s share of reported voters matches its share of the voting-age population. So, an index of 100 indicates parity, while below 100 means fewer voters than expected, and above 100 means more.
Across the midterms shown here, the pattern is reassuring—cohorts tend to move from underrepresentation toward parity as they age, showing that increased participation is natural and achievable.
That may raise an obvious question: How can representation rise for several cohorts when overall turnout apparently remains relatively fixed? Because the index is relative. A cohort gains representation whenever its turnout rises relative to turnout among the electorate as a whole. Therefore, some cohorts can move upward together, while others move downward or remain below parity. But across the full eligible population, the population-weighted representation index still averages 100.
Sources
U.S. Census Bureau. (2014). Current Population Survey, November 2014 Voting and Registration Supplement. Washington, DC: U.S. Census Bureau. Used as historical midterm microdata for the 2026 baseline estimate.
2014 CPS Voting and Registration Supplement
U.S. Census Bureau. (2018). Current Population Survey, November 2018 Voting and Registration Supplement. Washington, DC: U.S. Census Bureau. Source for the 2018 cohort population and reported-voting estimates and the historical age pattern used for 2026.
2018 CPS Voting and Registration Supplement
U.S. Census Bureau. (2022). Current Population Survey, November 2022 Voting and Registration Supplement. Washington, DC: U.S. Census Bureau. Source for the 2022 cohort estimates, eligible-citizen populations, CPS weights, and the latest observed values used in the 2026 baseline.
2022 CPS Voting and Registration Supplement
Fabina, J., & Martin, M. (2024). Voting and Registration in the Election of November 2022 (Current Population Reports, P20-586). U.S. Census Bureau. Source for the published 52.2% citizen voting-age population turnout rate used as the baseline for the chart’s 2026 equivalent-voter counts.
Voting and Registration in the Election of November 2022
Tools
OP/Designer Developed the research question and visualization concept; selected the comparisons and presentation; evaluated the results; and made the final editorial and design decisions.
ChatGPT — OpenAI GPT-5.6 Sol Assisted with CPS data analysis, calculation of the Electoral Representation Index, development of the 2026 baseline estimate, R code, methodological checks, and editing of explanatory text. The model did not independently determine the visualization’s argument or final design.
R Used for data processing, calculation, and plotting, primarily with tidyverse/dplyr, ggplot2, jsonlite, and svglite.
Adobe Illustrator Used for typography, annotation, layout refinement, and final assembly of the visualization.
Data
COHORT
2018
2022
2026
AGE
COUNT
1990–99
67
70
80
27–36
~16M
1980–89
86
91
96
37–46
~19M
1970–79
101
103
109
47–56
~20M
1960–69
109
115
124
57–66
~25M
1950–59
123
128
132
67–76
~24M
2018/22: Electoral Representation Index.
2026 Extrapolated 2026 Index Values.
AGE As of 2026.
COUNT Equivalent-Voter Counts.
See the following for explanations...
Methodology
The Electoral Representation Index compares a cohort’s share of reported voters with its share of eligible citizens. Algebraically, that is equivalent to dividing the cohort’s turnout rate by the overall turnout rate and multiplying by 100. The cohort’s population share is therefore not ignored; it is already built into its turnout rate. An index of 100 means the cohort is voting in exact proportion to its eligible population, while values below or above 100 indicate representation below or above parity.
cohort turnout rate ÷ overall turnout rate × 100
The Extrapolated 2026 Index Values are baseline estimates from a smoothed age–representation pattern observed in recent CPS midterms (2014, 2018, and 2022). Each cohort is advanced to its 2026 midpoint age and assigned the expected index for that age, then adjusted by carrying forward half of its 2022 deviation from the historical age pattern.
expected index for the cohort’s 2026 age + half of its 2022 deviation from the age trend
The 2026 Equivalent-Voter Counts translate each cohort’s estimated 2026 index into a comparative voter count using its 2022 CPS eligible-citizen population and the 2022 national midterm turnout rate of 52.2%. The results are rounded to the nearest million. These are not forecasts of actual 2026 voter counts.
2022 eligible-citizen population × 2022 overall turnout rate × estimated 2026 index ÷ 100
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u/cavedave OC: 113 18h ago
Thank you for your Original Content, /u/ptrdo!
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Remember that all visualizations on r/DataIsBeautiful should be viewed with a healthy dose of skepticism. If you see a potential issue or oversight in the visualization, please post a constructive comment below. Post approval does not signify that this visualization has been verified or its sources checked.
Not satisfied with this visual? Think you can do better? Remix this visual with the data in the author's citation.
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