When rebellious students massed at Berkeley's Sproul Hall Plaza last December, how many were there? Police estimated 7,000 to 10,000, and the newspapers dutifully reported the figure. But one reader was dissatisfied. "Estimating the size of a crowd may be the last area of fantasy in the newspaper business," observed Herbert A. Jacobs, 63, a longtime Wisconsin newspaperman who now lectures at the University of California. Jacobs set out to make a more scientific calculation.
First, he bought an enlarged aerial photograph of the mob scene, ruled it off in 1-in. squares, and used a magnifying glass to count heads. After four hours of eye-wracking work, he reached the total: 2,804—less than half of the swollen newspaper estimates. To find a mathematical short cut to more precise estimation, he showed up at other rallies, noted that the plaza was divided into 22-ft. squares. By counting the number of students in several squares and dividing, he was able to compute the average area occupied by an individual. This varied, he deduced, from a minimum of 4 sq. ft. in a tightly packed crowd to a maximum of 9.5 sq. ft. in a loosely knit one.
Then, by doing a little arithmetic, Jacobs arrived at what he calls the "Jacobs Crowd Formula": pace off the length and breadth of any crowd, add the two figures, multiply by seven for a slack crowd, by ten for a dense one.
Applying his formula to later rallies and checking it against photographs that he himself took, Jacobs discovered that such present-day spellbinders as Stokely Carmichael and Bettina Aptheker were not drawing nearly so well as the estimates would indicate. Once again, he had shown that reporters from the newspapers were doubling and tripling actual attendance.
Jacob admits that his formula is not flawless. Some crowds will not conform to the norm. If a crowd is composed primarily of women, for instance, some allowance must be made for greater hip girth. Or if the crowd is largely coeducational, he adds, it is conceivable that people might press closer together just for the fun of it.