Congressional seats are allocated to states based on how many inhabitants they have, as tabulated in the census every 10 years. As recently as the 1940s, Illinois had 27 U.S. House members. Today, it has just 18 — and commensurately less clout in Washington. After the 2020 census, it will have no more than 17, and could drop to 16. Texas, by contrast, could go from 36 to 38. Each state’s electoral votes in presidential elections will change accordingly.