lol, like 2.5% of the USA are programmers and even if we say twice that number have experimented and taken programming classes, that's like 1 in 20 people who would even have ever encountered a for loop. This nsf report says ~70% of highschoolers have taken Algebra 2 or a more advanced math course, which is when sum notation is usually introduced. I think 70% is a little greater than 5%!