Rank | $100K to $150K Family Income Percentage ▼ | School District / Population |
1. | 45.8% | Davey Elementary School District / 99 |
2. | 39.2% | Brorson Elementary School District / 222 |
3. | 36.0% | Van Norman Elementary School District / 108 |
4. | 31.0% | Montana City Elementary School District / 2,543 |
5. | 30.0% | Spring Creek Elementary School District / 86 |
6. | 29.0% | Miami Elementary School District / 112 |
7. | 27.6% | Clancy Elementary School District / 2,569 |
8. | 27.0% | Malmborg Elementary School District / 133 |
9. | 26.9% | Melville Elementary School District / 242 |
10. | 26.3% | Biddle Elementary School District / 70 |
11. | 26.1% | Birney Elementary School District / 73 |
12. | 26.0% | Creston Elementary School District / 1,060 |
13. | 25.0% | Wisdom Elementary School District / 283 |
13. | 25.0% | Landusky Elementary School District / 55 |
15. | 24.6% | Culbertson Elementary School District / 1,019 |
16. | 24.4% | Target Range Elementary School District / 3,277 |
17. | 24.3% | Deep Creek Elementary School District / 149 |
18. | 24.1% | Jefferson High School District / 7,804 |
19. | 23.3% | Culbertson High School District / 921 |
20. | 23.1% | Carter Elementary School District / 143 |
21. | 22.7% | Winifred K-12 Schools / 489 |
22. | 22.3% | Independent Elementary School District / 2,555 |
23. | 22.2% | Alzada Elementary School District / 160 |
24. | 21.7% | Ringling Elementary School District / 94 |
25. | 21.3% | Seeley Lake Elementary School District / 1,614 |
26. | 21.1% | Blue Creek Elementary School District / 2,190 |
27. | 20.6% | Baker K-12 Schools / 2,302 |
28. | 20.5% | Frenchtown K-12 Schools / 5,970 |
29. | 20.3% | Ophir Elementary School District / 1,074 |
30. | 20.3% | East Glacier Park Elementary School District / 850 |
31. | 19.6% | Colstrip Elementary School District / 2,351 |
31. | 19.6% | Colstrip High School District / 2,351 |
33. | 19.1% | Anderson Elementary School District / 1,129 |
34. | 18.6% | Joliet High School District / 2,178 |
35. | 18.5% | Clinton Elementary School District / 1,666 |
36. | 18.5% | Belfry K-12 Schools / 553 |
37. | 18.1% | Froid Elementary School District / 443 |
37. | 18.1% | Froid High School District / 443 |
39. | 17.9% | Morin Elementary School District / 533 |
40. | 17.7% | Reichle Elementary School District / 116 |
41. | 17.5% | Florence-Carlton K-12 Schools / 5,688 |
42. | 17.3% | Kircher Elementary School District / 728 |
43. | 17.3% | Cottonwood Elementary School District / 356 |
44. | 17.1% | La Motte Elementary School District / 734 |
45. | 16.8% | Cut Bank High School District / 4,451 |
45. | 16.8% | Cut Bank Elementary School District / 4,451 |
47. | 16.8% | Melstone High School District / 424 |
48. | 16.7% | Upper West Shore Elementary School District / 757 |
48. | 16.7% | Pass Creek Elementary School District / 82 |
48. | 16.7% | East Helena Elementary School District / 8,387 |
51. | 16.6% | Kinsey Elementary School District / 416 |
52. | 16.3% | Wise River Elementary School District / 294 |
53. | 16.1% | Pine Creek Elementary School District / 367 |
54. | 16.1% | Cascade Elementary School District / 1,757 |
55. | 15.9% | Cottonwood Elementary School District / 236 |
56. | 15.8% | Trail Creek Elementary School District / 64 |
57. | 15.7% | Manhattan Elementary School District / 2,523 |
58. | 15.5% | Lolo Elementary School District / 3,934 |
59. | 15.2% | Elder Grove Elementary School District / 2,053 |
60. | 15.0% | Monforton Elementary School District / 1,807 |
61. | 15.0% | Hall Elementary School District / 259 |
62. | 15.0% | Helena High School District / 58,464 |
63. | 15.0% | Swan River Elementary School District / 1,685 |
64. | 14.9% | Park City Elementary School District / 2,206 |
65. | 14.9% | Centerville Elementary School District / 1,526 |
65. | 14.9% | Lambert High School District / 384 |
67. | 14.9% | Helena Elementary School District / 48,201 |
68. | 14.7% | Huntley Project K-12 Schools / 3,750 |
69. | 14.6% | Bear Paw Elementary School District / 122 |
70. | 14.5% | Ramsay Elementary School District / 1,040 |
71. | 14.3% | Trinity Elementary School District / 1,242 |
72. | 14.3% | Jackson Elementary School District / 171 |
73. | 14.3% | Bozeman High School District / 58,563 |
74. | 14.2% | Glendive Elementary School District / 6,042 |
75. | 14.1% | Bozeman Elementary School District / 51,961 |
76. | 14.0% | West Yellowstone K-12 School District / 1,493 |
77. | 13.9% | Rau Elementary School District / 271 |
78. | 13.9% | Shepherd High School District / 2,920 |
78. | 13.9% | Shepherd Elementary School District / 2,920 |
80. | 13.9% | De Smet Elementary School District / 580 |
81. | 13.8% | Park City High School District / 2,065 |
82. | 13.8% | Fair-Mont-Egan Elementary School District / 1,130 |
83. | 13.8% | Box Elder High School District / 335 |
83. | 13.8% | Box Elder Elementary School District / 335 |
83. | 13.8% | Red Lodge High School District / 4,012 |
86. | 13.8% | Columbus High School District / 3,493 |
87. | 13.7% | Whitefish Elementary School District / 14,029 |
88. | 13.6% | Cayuse Prairie Elementary School District / 2,511 |
89. | 13.6% | Belgrade Elementary School District / 19,573 |
90. | 13.6% | Whitefish High School District / 14,617 |
91. | 13.5% | Manhattan High School District / 3,940 |
92. | 13.5% | Lincoln K-12 Schools / 978 |
93. | 13.5% | Carter County High School District / 1,237 |
94. | 13.5% | Hellgate Elementary School District / 10,647 |
94. | 13.5% | Belgrade High School District / 19,773 |
96. | 13.3% | Red Lodge Elementary School District / 3,445 |
96. | 13.3% | Hysham K-12 Schools / 912 |
98. | 13.2% | Bynum Elementary School District / 161 |
99. | 13.2% | Kalispell Elementary School District / 28,562 |
100. | 13.2% | Ekalaka Elementary School District / 958 |
101. | 13.1% | Centerville High School District / 1,474 |
101. | 13.1% | Rapelje High School District / 351 |
103. | 13.0% | Spring Creek Elementary School District / 78 |
104. | 13.0% | Columbus Elementary School District / 3,352 |
105. | 12.9% | Shields Valley Elementary School District / 1,731 |
105. | 12.9% | Shields Valley High School District / 1,731 |
107. | 12.9% | Willow Creek Elementary School District / 212 |
108. | 12.9% | Big Timber Elementary School District / 2,819 |
108. | 12.9% | Pioneer Elementary School District / 792 |
110. | 12.9% | Billings High School District / 122,509 |
111. | 12.7% | Missoula High School District / 97,049 |
112. | 12.7% | Billings Elementary School District / 104,681 |
112. | 12.7% | Laurel Elementary School District / 10,532 |
114. | 12.5% | Hobson K-12 Schools / 875 |
115. | 12.4% | Woodman Elementary School District / 580 |
116. | 12.4% | Lewistown Elementary School District / 8,714 |
116. | 12.4% | Vaughn Elementary School District / 1,040 |
118. | 12.3% | Geyser Elementary School District / 202 |
119. | 12.3% | Cascade High School District / 2,659 |
120. | 12.3% | Lambert Elementary School District / 407 |
121. | 12.3% | Fergus High School District / 8,858 |
122. | 12.2% | Havre High School District / 13,197 |
123. | 12.2% | Sidney High School District / 6,811 |
124. | 12.2% | Paradise Elementary School District / 392 |
125. | 12.2% | Hinsdale Elementary School District / 382 |
126. | 12.1% | Sweet Grass County High School District / 3,567 |
127. | 12.0% | Dawson High School District / 8,074 |
128. | 12.0% | Troy Elementary School District / 2,612 |
129. | 12.0% | Dodson High School District / 331 |
130. | 12.0% | Havre Elementary School District / 12,764 |
131. | 11.8% | Cooke City Elementary School District / 77 |
132. | 11.7% | Hamilton K-12 Schools / 11,767 |
132. | 11.7% | Forsyth Elementary School District / 2,497 |
134. | 11.7% | Missoula Elementary School District / 70,583 |
135. | 11.7% | Joliet Elementary School District / 1,624 |
136. | 11.7% | Forsyth High School District / 2,531 |
137. | 11.6% | Bigfork High School District / 7,893 |
138. | 11.6% | Deer Park Elementary School District / 765 |
139. | 11.5% | Swan Valley Elementary School District / 403 |
139. | 11.5% | Superior K-12 Schools / 2,370 |
139. | 11.5% | Willow Creek High School District / 169 |
142. | 11.5% | Canyon Creek Elementary School District / 1,807 |
143. | 11.5% | Fishtail Elementary School District / 366 |
144. | 11.5% | Medicine Lake K-12 Schools / 723 |
145. | 11.4% | Circle Elementary School District / 1,213 |
146. | 11.4% | Rapelje Elementary School District / 233 |
147. | 11.3% | Name N/A / 852,731 |
147. | 11.3% | Flathead High School District / 52,794 |
149. | 11.3% | Hinsdale High School District / 418 |
150. | 11.3% | Glasgow K-12 Schools / 4,534 |
150. | 11.3% | Laurel High School District / 10,015 |
152. | 11.3% | Melstone Elementary School District / 619 |
153. | 11.3% | Belt High School District / 2,020 |
154. | 11.2% | Helena Flats Elementary School District / 1,534 |
155. | 11.1% | Molt Elementary School District / 184 |
156. | 11.0% | Sidney Elementary School District / 6,244 |
157. | 10.9% | Rocky Boy High School District / 1,498 |
158. | 10.9% | Bigfork Elementary School District / 6,078 |
159. | 10.8% | Absarokee Elementary School District / 1,841 |
160. | 10.8% | Geyser High School District / 334 |
161. | 10.7% | Golden Ridge Elementary School District / 180 |
162. | 10.6% | Denton High School District / 671 |
162. | 10.6% | Roberts K-12 Schools / 688 |
162. | 10.6% | Denton Elementary School District / 664 |
165. | 10.6% | Ronan High School District / 8,304 |
165. | 10.6% | Ronan Elementary School District / 8,304 |
167. | 10.5% | Troy High School District / 3,222 |
168. | 10.4% | Custer County High School District / 11,129 |
169. | 10.3% | Butte High School District / 32,714 |
170. | 10.3% | Three Forks Elementary School District / 2,639 |
171. | 10.2% | Fairfield Elementary School District / 1,115 |
172. | 10.2% | Stanford K-12 Schools / 857 |
173. | 10.2% | Butte Elementary School District / 31,449 |
174. | 10.1% | Circle High School District / 1,747 |
174. | 10.1% | Drummond High School District / 1,207 |
176. | 10.0% | Fairfield High School District / 1,888 |
177. | 10.0% | Augusta Elementary School District / 496 |
178. | 9.9% | Terry K-12 Schools / 1,004 |
179. | 9.9% | Great Falls Elementary School District / 72,584 |
180. | 9.9% | Great Falls High School District / 72,659 |
181. | 9.9% | Amsterdam Elementary School District / 1,390 |
182. | 9.9% | Plentywood K-12 Schools / 2,487 |
183. | 9.8% | Augusta High School District / 639 |
184. | 9.8% | Divide Elementary School District / 138 |
185. | 9.8% | Miles City Elementary School District / 9,488 |
186. | 9.7% | St. Regis K-12 Schools / 1,055 |
187. | 9.7% | Garfield County High School District / 1,135 |
188. | 9.5% | Thompson Falls Elementary School District / 3,096 |
188. | 9.5% | Bainville K-12 Schools / 335 |
188. | 9.5% | Thompson Falls High School District / 3,096 |
191. | 9.5% | Harrison K-12 Schools / 927 |
192. | 9.5% | Jordan Elementary School District / 640 |
193. | 9.4% | Lone Rock Elementary School District / 3,252 |
194. | 9.3% | Belt Elementary School District / 2,043 |
195. | 9.3% | Chester-Joplin-Inverness Elementary School District / 2,185 |
196. | 9.3% | Greenfield Elementary School District / 598 |
197. | 9.2% | Beaverhead County High School District / 8,478 |
198. | 9.2% | Pendroy Elementary School District / 334 |
199. | 9.1% | Three Forks High School District / 2,592 |
200. | 9.1% | Westby K-12 Schools / 358 |
200. | 9.1% | Dupuyer Elementary School District / 309 |
200. | 9.1% | Zurich Elementary School District / 263 |
203. | 9.0% | Simms High School District / 3,100 |
204. | 8.9% | Chester-Joplin-Inverness High School District / 2,290 |
205. | 8.9% | Big Sandy Elementary School District / 1,121 |
206. | 8.9% | Peerless K-12 Schools / 137 |
206. | 8.9% | King Colony Elementary School District / 140 |
208. | 8.9% | Potomac Elementary School District / 1,138 |
209. | 8.8% | Sand Springs Elementary School District / 85 |
209. | 8.8% | Elysian Elementary School District / 488 |
211. | 8.8% | Gardiner High School District / 1,787 |
211. | 8.8% | Nashua K-12 Schools / 935 |
213. | 8.8% | Columbia Falls Elementary School District / 13,994 |
213. | 8.8% | Raynesford Elementary School District / 132 |
215. | 8.8% | Anaconda Elementary School District / 8,737 |
216. | 8.8% | Dodson Elementary School District / 276 |
217. | 8.7% | Drummond Elementary School District / 948 |
217. | 8.7% | Rosebud Elementary School District / 375 |
217. | 8.7% | Luther Elementary School District / 441 |
217. | 8.7% | Anaconda High School District / 8,782 |
217. | 8.7% | Auchard Creek Elementary School District / 143 |
217. | 8.7% | Olney-Bissell Elementary School District / 927 |
223. | 8.7% | Ennis K-12 Schools / 2,563 |
224. | 8.6% | West Valley Elementary School District / 2,822 |
224. | 8.6% | Gardiner Elementary School District / 1,710 |
226. | 8.6% | Broadview Elementary School District / 871 |
227. | 8.6% | Columbia Falls High School District / 14,405 |
228. | 8.4% | Lockwood Elementary School District / 7,389 |
229. | 8.4% | Polson High School District / 10,702 |
230. | 8.3% | Melrose Elementary School District / 87 |
231. | 8.3% | Valier High School District / 1,417 |
232. | 8.3% | Absarokee High School District / 2,256 |
233. | 8.3% | Boulder Elementary School District / 2,428 |
234. | 8.3% | Rosebud High School District / 398 |
235. | 8.3% | Roy K-12 Schools / 348 |
236. | 8.2% | Dillon Elementary School District / 7,428 |
237. | 8.2% | Kila Elementary School District / 1,231 |
238. | 8.1% | White Sulphur Springs High School District / 1,628 |
239. | 8.1% | Browning High School District / 8,960 |
240. | 8.1% | Broadview High School District / 937 |
241. | 8.1% | Valier Elementary School District / 1,108 |
242. | 8.1% | Plains High School District / 3,352 |
243. | 8.0% | Deer Creek Elementary School District / 1,622 |
244. | 8.0% | Avon Elementary School District / 177 |
244. | 8.0% | Wibaux K-12 Schools / 922 |
246. | 8.0% | Lavina K-12 Schools / 532 |
246. | 8.0% | Gallatin Gateway Elementary School District / 1,489 |
248. | 7.9% | Fairview High School District / 1,413 |
249. | 7.9% | Sunset Elementary School District / 174 |
250. | 7.9% | Somers Elementary School District / 4,396 |
251. | 7.9% | Polson Elementary School District / 9,518 |
252. | 7.8% | Choteau High School District / 3,107 |
253. | 7.7% | Stevensville High School District / 9,879 |
254. | 7.7% | Eureka Elementary School District / 4,157 |
255. | 7.7% | Plains Elementary School District / 2,960 |
256. | 7.7% | White Sulphur Springs Elementary School District / 1,482 |
257. | 7.7% | Sheridan Elementary School District / 1,783 |
258. | 7.6% | Plevna K-12 Schools / 355 |
259. | 7.6% | Camas Prairie Elementary School District / 249 |
260. | 7.5% | Smith Valley Elementary School District / 1,761 |
261. | 7.5% | Name N/A / 300 |
262. | 7.5% | Townsend K-12 Schools / 4,335 |
262. | 7.5% | Sun River Valley Elementary School District / 2,060 |
264. | 7.4% | Sunburst K-12 Schools / 1,300 |
265. | 7.4% | Libby K-12 Schools / 10,055 |
266. | 7.2% | Conrad High School District / 3,333 |
267. | 7.2% | Choteau Elementary School District / 2,612 |
268. | 7.1% | Helmville Elementary School District / 230 |
269. | 7.1% | Scobey K-12 Schools / 1,346 |
270. | 7.1% | Fairview Elementary School District / 1,403 |
271. | 7.0% | S H Elementary School District / 121 |
272. | 7.0% | Vida Elementary School District / 534 |
273. | 6.9% | Richey Elementary School District / 381 |
274. | 6.9% | Rocky Boy Elementary School District / 2,389 |
275. | 6.8% | Sheridan High School District / 2,075 |
276. | 6.8% | Stevensville Elementary School District / 6,627 |
276. | 6.8% | Browning Elementary School District / 8,110 |
278. | 6.8% | Lincoln County High School District / 5,421 |
279. | 6.7% | Fort Benton High School District / 1,994 |
280. | 6.7% | Alberton K-12 Schools / 1,100 |
281. | 6.7% | Pine Grove Elementary School District / 100 |
282. | 6.7% | Shelby Elementary School District / 3,521 |
282. | 6.7% | Chinook High School District / 2,407 |
284. | 6.6% | Shelby High School District / 3,810 |
285. | 6.6% | Reedpoint High School District / 501 |
286. | 6.6% | Charlo Elementary School District / 1,342 |
287. | 6.6% | Park High School District / 12,686 |
288. | 6.5% | Roundup Elementary School District / 3,797 |
289. | 6.5% | Swan Lake-Salmon Elementary School District / 218 |
290. | 6.5% | Galata Elementary School District / 289 |
291. | 6.4% | Livingston Elementary School District / 10,306 |
291. | 6.4% | Powder River County High School District / 1,691 |
293. | 6.4% | Marion Elementary School District / 840 |
294. | 6.4% | Conrad Elementary School District / 3,221 |
295. | 6.4% | Arlee High School District / 2,377 |
295. | 6.4% | Arlee Elementary School District / 2,377 |
295. | 6.4% | Cardwell Elementary School District / 481 |
298. | 6.3% | Roundup High School District / 3,958 |
299. | 6.2% | Victor K-12 Schools / 3,644 |
300. | 6.2% | Wolf Point Elementary School District / 3,715 |
301. | 6.1% | Wolf Point High School District / 4,281 |
302. | 6.1% | Hot Springs High School District / 1,668 |
303. | 6.1% | Richey High School District / 473 |
304. | 6.1% | Basin Elementary School District / 264 |
304. | 6.1% | Fort Benton Elementary School District / 1,699 |
306. | 6.0% | Greycliff Elementary School District / 284 |
307. | 6.0% | Saco High School District / 388 |
308. | 5.9% | Evergreen Elementary School District / 5,740 |
309. | 5.8% | Yaak Elementary School District / 148 |
310. | 5.8% | Hot Springs Elementary School District / 1,419 |
311. | 5.8% | Corvallis K-12 Schools / 7,291 |
312. | 5.7% | Winnett K-12 Schools / 512 |
312. | 5.7% | Arrowhead Elementary School District / 1,852 |
314. | 5.7% | Reedpoint Elementary School District / 549 |
314. | 5.7% | Name N/A / 842 |
316. | 5.7% | Twin Bridges K-12 Schools / 1,351 |
317. | 5.7% | Saco Elementary School District / 424 |
317. | 5.7% | Hardin High School District / 8,013 |
319. | 5.7% | Fromberg K-12 Schools / 1,105 |
320. | 5.6% | Chinook Elementary School District / 2,022 |
321. | 5.6% | Charlo High School District / 1,976 |
321. | 5.6% | Frontier Elementary School District / 566 |
323. | 5.5% | Broadus Elementary School District / 1,363 |
324. | 5.4% | Lima K-12 Schools / 409 |
325. | 5.4% | Darby K-12 Schools / 3,077 |
326. | 5.4% | Big Sandy High School District / 2,034 |
327. | 5.3% | Philipsburg K-12 Schools / 1,673 |
328. | 5.2% | Ashland Elementary School District / 1,156 |
329. | 5.2% | Elliston Elementary School District / 291 |
330. | 5.0% | McCormick Elementary School District / 344 |
331. | 5.0% | North Star High School District / 1,214 |
332. | 5.0% | Custer K-12 Schools / 400 |
332. | 5.0% | Trego Elementary School District / 660 |
334. | 4.9% | Lodge Grass Elementary School District / 1,921 |
334. | 4.9% | St. Ignatius K-12 Schools / 3,138 |
336. | 4.9% | Hardin Elementary School District / 8,993 |
337. | 4.8% | Lodge Grass High School District / 2,319 |
338. | 4.8% | Opheim K-12 Schools / 415 |
339. | 4.7% | Turner Elementary School District / 312 |
339. | 4.7% | Turner High School District / 321 |
341. | 4.7% | Poplar High School District / 3,329 |
341. | 4.7% | Hawks Home Elementary School District / 119 |
341. | 4.7% | Poplar Elementary School District / 3,329 |
341. | 4.7% | Lustre Elementary School District / 162 |
345. | 4.6% | Nye Elementary School District / 175 |
346. | 4.4% | Wolf Creek Elementary School District / 407 |
347. | 4.3% | Deer Lodge Elementary School District / 5,878 |
348. | 4.3% | Wyola Elementary School District / 398 |
349. | 4.2% | Highwood High School District / 482 |
350. | 4.2% | Noxon Elementary School District / 1,313 |
351. | 4.2% | Harlowton Elementary School District / 1,669 |
352. | 4.1% | Savage High School District / 520 |
353. | 4.1% | Savage Elementary School District / 499 |
354. | 4.1% | Valley View Elementary School District / 427 |
355. | 4.1% | Powell County High School District / 7,151 |
356. | 4.0% | Malta K-12 Schools / 3,097 |
357. | 4.0% | Lame Deer High School District / 5,339 |
358. | 3.9% | Springhill Elementary School District / 131 |
358. | 3.9% | Cottonwood Elementary School District / 149 |
360. | 3.9% | Harlowton High School District / 1,772 |
361. | 3.8% | Noxon High School District / 2,229 |
362. | 3.7% | Highwood Elementary School District / 540 |
363. | 3.6% | Lame Deer Elementary School District / 3,168 |
364. | 3.5% | North Star Elementary School District / 1,082 |
365. | 3.4% | Trout Creek Elementary School District / 916 |
366. | 3.4% | Fortine Elementary School District / 604 |
367. | 3.3% | Bonner Elementary School District / 2,365 |
368. | 3.2% | Whitehall High School District / 3,725 |
369. | 3.1% | Alder Elementary School District / 292 |
370. | 2.9% | Power Elementary School District / 520 |
371. | 2.9% | Power High School District / 525 |
371. | 2.9% | Dixon Elementary School District / 634 |
373. | 2.9% | Pryor Elementary School District / 961 |
373. | 2.9% | Plenty Coups High School District / 961 |
375. | 2.8% | Bloomfield Elementary School District / 99 |
376. | 2.4% | Dutton/Brady K-12 Schools / 945 |
377. | 1.8% | Ulm Elementary School District / 753 |
378. | 1.7% | Harlem Elementary School District / 2,676 |
379. | 1.7% | Geraldine Elementary School District / 652 |
380. | 1.6% | Lindsay Elementary School District / 387 |
381. | 1.6% | Harlem High School District / 2,771 |
382. | 1.5% | Geraldine High School District / 713 |
383. | 1.4% | Bridger K-12 Schools / 1,205 |
384. | 1.3% | Frazer High School District / 586 |
385. | 1.2% | Whitehall Elementary School District / 3,168 |
386. | 1.1% | Hays-Lodge Pole K-12 Schools / 1,016 |
387. | 1.0% | Ryegate K-12 Schools / 341 |
Please note that we only rank locations with '$100K to $150K Family Income Percentage' data. The rank above might not be a complete list. Locations without '$100K to $150K Family Income Percentage' data are not listed.
*ACS stands for U.S. Census American Community Survey. According to the U.S. Census, if the date is a range, you can interpret the data as an average of the period of time.