Tidy Tuesday: FIDE Chess Ratings

This week I was curious about the size of rating changes as chess players age. I expected to see that people lose more rating points as they age, but the reality is that rating is most volatile before people turn 20.

Code:

tuesdata <- tidytuesdayR::tt_load(2025, week = 38)

fide_ratings_august <- tuesdata$fide_ratings_august
fide_ratings_september <- tuesdata$fide_ratings_september

library(tidyverse)
library(ggtext)

fide <- inner_join(fide_ratings_august, 
                   fide_ratings_september,
                   by = c("name", "id", "fed", "sex", "bday"),
                   suffix = c("_aug", "_sep")) %>%
  mutate(age = 2025 - bday,
         rating_change = rating_sep - rating_aug) %>%
  filter(rating_change != 0,
         games_aug > 0,
         games_sep > 0) %>%
  mutate(value = case_when(
    rating_change >= 0 ~ "Gained rating",
    rating_change < 0 ~ "Lost rating"
  ))

t <- "**Chess Rating Change by Age**"
st <- "Each point represents a FIDE-rated player who<br>competed in both August and September 2025."
c <- "Created by @jessimoore.bsky.social  Source: ratings.fide.com"

bg <- "#E2DDD5"
text_color <- "#3B2F26"
values <- c("#887A6E", "#3B2F26")

plot <- ggplot(fide,
               aes(x = age,
                   y = rating_change,
                   colour = value),
               ) +
  geom_point(alpha = 0.15, size = 1) +
  annotate("richtext",
         x = 65, y = 340,
         label = t,
         size = 7,
         fill = bg,
         label.color = bg,
         color = text_color) +
  annotate("richtext",
         x = 70, y = 290,
         label = st,
         fill = bg,
         label.color = bg,
         color = text_color) +
  annotate("richtext",
         x = 76, y = -300,
         label = c,
         size = 2.5,
         fill = bg,
         label.color = bg,
         color = text_color) +
  scale_x_continuous(breaks = c(10,20,30,40,50,60,70,80,90)) +
  scale_y_continuous(breaks = c(-250, -200, -150, -100, -50, 0, 50, 100, 150, 200, 250)) +
  scale_color_manual(values = values) +
  guides(color = guide_legend(override.aes = list(alpha = 1))) +
  labs(x = "Age", y = "Rating change",
       color = NULL) +
  theme_minimal() +
  theme(panel.grid = element_line(color = "#887A6E", linewidth = 0.05),
        plot.title = element_text(face = "bold"),
        legend.position = "inside",
        legend.position.inside = c(0.84,0.765),
        legend.text = element_text(size = 10),
        text = element_text(color = text_color),
        axis.text = element_text(color = text_color, size = 11),
        axis.title = element_text(size = 12),
        plot.background = element_rect(fill = bg),
        panel.background = element_rect(fill = bg))