We document the imbalance among the areas of the Math Classification Scheme. Data refer to two datasets: 1. MR entries 1991-1996, sorted by unique primary classification number 2. MR entries 1940-1997, assigned (multiple) primary and secondary classifications. (Note: due to change in classification schemes, the reported numbers are undercounts of appropriate measures, e.g. "section 11" should refer to "sec.10 + sec.11") Possible classifications are 2-digit, 3-digit, or 5-digit. Twodigit: N = 61 mean size in small dataset: 4046 items/2dig min: Smallest areas in small dataset, together with number of primary+secondary entries in large dataset: 85 288 5206 19 336 2816 [anomolously small] 40 480 8068 median: #31 is 57 with 2528 entries. 38 areas (62%) are smaller than mean size, 23 larger. Item 39 is 54 (General Topology). max: Largest areas in small dataset, together with number of primary+secondary entries in large dataset: 81 14204 88296 65 13372 92803 35 12803 94355 68 12374 63231 62 11903 78723 90 10915 76362 Half of the small-database items are in the top 12 largest 2digit fields (those 6 plus 58,93,60,5,34,11), only 20% of the available 2digit fields [big 10 shown below; 34=DE, 11=NumThy][next is 13% less!] Threedigit: N = 535 mean size in small dataset: 461 items/3dig min: 53Z, 11Z are empty (but 11Z50 now has 271 primary&secondary) median: #267 is 60D with only 185 entries, that is, most of the 3digit areas are small. Fully 383 are smaller than mean size (72%); only 152 are larger than mean. Item 384 is 20E. max: Largest areas in small dataset, together with number of primary+secondary entries in large dataset: 81T 6647 16020 58F 6191 40763 68Q 5838 26912 05C 5551 31562 01A 5126 28404 90C 5107 32199 93B 3718 18239 83C 3358 16K [these not shown below] 53C 3030 24 35Q 2610 22 41A 2601 20 03B 2382 18 Half of the small-database items are in the top 55 largest 3digit fields, only 10% of the available 3digit fields Fivedigit: N = 4819 mean size in small dataset: 51 items/5dig min: Fully 500 of these have zero entries in the small database! This includes 144 "nn-XX" plus 223 "nnA00" plus 33 "nnA99" plus the 100 fields shown at bottom. median: #2410 is 45F10 with 18 entries. 3577 areas (74%) are smaller than mean size, 1242 larger. Item 3578 is 94A15 max: Largest areas in small dataset, together with number of primary+secondary entries in large dataset: 01A70 2163 10465 1 81T40 1973 4997 12 81T30 1341 3972 11 62G05 1098 5103 6 58F07 1044 6270 3 90C30 1004 7048 13 60K25 966 5833 5 58F13 831 6089 4 62M10 782 4547 7 68U05 777 2575 9 81T13 762 2932 10 30C45 757 3008 2 65N30 750 6215 8 Half of the small-database items are in the top 411 largest 5digit fields, only 8.5% of the available 5digit fields These are the large areas mentioned: 01-XX History and biography * 01Axx History of mathematics and mathematicians ** 01A70 Biographies, obituaries, personalia, bibliographies 05-XX Combinatorics * 05Cxx Graph theory 30-XX Functions of a complex variable * 30Cxx Geometric function theory 35-XX Partial differential equations 58-XX Global analysis, analysis on manifolds * 58Fxx Ordinary differential equations on manifolds; dynamical systems ** 58F07 Completely integrable systems (including systems with an infinite number of degrees of freedom) ** 58F13 Strange attractors; chaos and other pathologies 60-XX Probability theory and stochastic processes * 60Kxx Special processes ** 60K25 Queueing theory, See also {68M20, 90B22} 62-XX Statistics * 62Gxx Nonparametric inference ** 62G05 Estimation * 62Mxx Inference from stochastic processes ** 62M10 Time series, auto-correlation, regression, etc 65-XX Numerical analysis * 65Nxx Partial differential equations, boundary value problems ** 65N30 Finite elements, Rayleigh-Ritz and Galerkin methods, finite methods 68-XX Computer science * 68Qxx Theory of computing * 68Uxx Computing methodologies ** 68U05 Computer graphics; computational geometry, See also {65Y25} 81-XX Quantum Theory * 81Txx Quantum field theory; related classical field theories ** 81T13 Yang-Mills and other gauge theories, See also {53C07, ** 81T30 String and superstring theories; other extended objects , ** 81T40 Two-dimensional field theories, conformal field theories, etc. 90-XX Economics, operations research, programming, games * 90Cxx Mathematical programming, see also {49Mxx, 65Kxx} ** 90C30 Nonlinear programming 93-XX Systems theory; control * 93Bxx Controllability, observability, and system structure 94-XX Information and communication, circuits * 94Axx Communication, information ** 94A15 Information theory, general, See also {62B10} Empty Fivedigits: [030520, 110570, 112107, 112605, 120710, 121017, 140510, 140535, 140870, 141240, 170125, 170290, 170337, 170355, 170360, 180123, 180305, 180520, 180605, 180630, 180735, 190115, 190340, 191005, 191035, 191114, 191241, 201010, 201112, 201126, 260540, 320381, 321010, 321405, 321410, 330325, 330330, 330335, 330340, 330425, 330430, 330435, 330440, 330490, 340350, 351935, 400515, 461440, 461455, 461460, 470310, 471440, 471920, 491349, 491440, 510405, 510430, 511010, 511205, 511210, 511220, 532605, 540635, 551315, 551625, 552005, 552120, 552130, 571430, 571730, 571737, 571750, 571791, 571805, 571812, 572030, 572035, 580546, 601140, 620735, 652005, 700205, 700705, 700715, 700720, 700725, 701040, 730510, 730610, 730620, 730625, 760420, 760435, 812219, 860104, 900150, 920710, 920720, 920740, 930523] Primary+second counts in large database: [39, 22, 3, 163, 21, ..., 9] Twodigit sorted by size in small dataset: [85, 288], [19, 336], [40, 480], [44, 505], [8, 509], [86, 530], [4, 538], [43, 542], [18, 641], [31, 663], [12, 668], [80, 757], [39, 780], [45, 885], [78, 1038], [33, 1187], [55, 1256], [28, 1379], [13, 1465], [6, 1506], [52, 1563], [22, 1572], [26, 1612], [51, 1674], [70, 1849], [15, 1960], [0, 2127], [42, 2134], [92, 2269], [17, 2420], [57, 2528], [94, 2529], [41, 2650], [32, 2837], [14, 3152], [16, 3426], [49, 3478], [30, 3829], [54, 4103], [73, 4663], [53, 4664], [83, 5009], [82, 5050], [1, 5211], [47, 5580], [20, 5786], [3, 5878], [46, 6104], [76, 6295], [11, 7245], [34, 7348], [5, 8392], [60, 9886], [93, 10013], [58, 10430], [90, 10915], [62, 11903], [68, 12374], [35, 12803], [65, 13372], [81, 14204]