## Interpretation of Incidence Rates Data

### Incidence Rate Report for Michigan by County

All Races (includes Hispanic), Both Sexes, Colon & Rectum, All Ages

Sorted by Rate

**Explanation of Column Headers**

**Incidence Rate (95% Confidence Interval)**- The incidence rate is based upon 100,000 people and is an annual rate (or average annual rate) based on the time period indicated. Rates are age-adjusted by 5-year age groups to the 2000 U.S. standard million population.

**Recent Trends** - This is an interpretation of the AAPC/APC:

**Rising**when 95% confidence interval of AAPC/APC is above 0.**Stable**when 95% confidence interval of AAPC/APC includes 0.**Falling**when 95% confidence interval of AAPC/APC is below 0.

**AAPC/APC (95% Confidence Interval)** - the change in rate over time

- Average Annual Percent Change - AAPCs are based upon APCs that were calculated by Joinpoint Regression Program
- Annual Percent Change - APCs calculated in SEER*Stat.

**Other Notes**

**Line by Line Interpretation of the Report**

#### Michigan^{5,10}

- Rate : The incidence rate is 40.7 # with a 95% confidence interval from 40.2 to 41.3 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -4.4 with a 95% confidence interval from -5.1 to -3.7.

#### US (SEER+NPCR)^{1,10}

- Rate : The incidence rate is 41.9 with a 95% confidence interval from 41.8 to 42.0 and 140,433 § average annual cases over 2008-2012.
- Recent Trend : The trend is falling because the trend is -3.9 with a 95% confidence interval from -4.7 to -3.0.

#### Gratiot County^{6,10}

- Rate : The incidence rate is 56.8 # with a 95% confidence interval from 47.7 to 67.3 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -9.2 with a 95% confidence interval from -24.0 to 8.5.

#### Schoolcraft County^{6,10}

- Rate : The incidence rate is 50.6 # with a 95% confidence interval from 34.1 to 73.8 and average annual cases over .
- Recent Trend : * Data has been suppressed to ensure confidentiality and stability of rate estimates. Counts are suppressed if fewer than 16 cases were reported in a specific area-sex-race category. If an average count of 3 is shown, the total number of cases for the time period is 16 or more which exceeds suppression threshold (but is rounded to 3).

#### Osceola County^{6,10}

- Rate : The incidence rate is 50.4 # with a 95% confidence interval from 39.6 to 63.5 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -4.4 with a 95% confidence interval from -26.6 to 24.5.

#### Alpena County^{6,10}

- Rate : The incidence rate is 50.1 # with a 95% confidence interval from 41.0 to 61.0 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 0.3 with a 95% confidence interval from -21.4 to 28.1.

#### Tuscola County^{6,10}

- Rate : The incidence rate is 49.4 # with a 95% confidence interval from 42.2 to 57.6 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -12.9 with a 95% confidence interval from -17.8 to -7.7.

#### St. Clair County^{6,10}

- Rate : The incidence rate is 48.4 # with a 95% confidence interval from 44.1 to 53.1 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -8.1 with a 95% confidence interval from -14.7 to -1.1.

#### Wayne County^{7,8}

- Rate : The incidence rate is 47.7 with a 95% confidence interval from 46.3 to 49.1 and 942 average annual cases over 2008-2012.
- Recent Trend : The trend is falling because the trend is -3.7 with a 95% confidence interval from -5.0 to -2.4.

#### Ontonagon County^{6,10}

- Rate : The incidence rate is 46.5 # with a 95% confidence interval from 30.0 to 72.3 and average annual cases over .
- Recent Trend : * Data has been suppressed to ensure confidentiality and stability of rate estimates. Counts are suppressed if fewer than 16 cases were reported in a specific area-sex-race category. If an average count of 3 is shown, the total number of cases for the time period is 16 or more which exceeds suppression threshold (but is rounded to 3).

#### Oscoda County^{6,10}

- Rate : The incidence rate is 46.4 # with a 95% confidence interval from 31.7 to 67.4 and average annual cases over .
- Recent Trend : * Data has been suppressed to ensure confidentiality and stability of rate estimates. Counts are suppressed if fewer than 16 cases were reported in a specific area-sex-race category. If an average count of 3 is shown, the total number of cases for the time period is 16 or more which exceeds suppression threshold (but is rounded to 3).

#### Berrien County^{6,10}

- Rate : The incidence rate is 45.8 # with a 95% confidence interval from 41.7 to 50.3 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -5.3 with a 95% confidence interval from -18.9 to 10.6.

#### Isabella County^{6,10}

- Rate : The incidence rate is 45.7 # with a 95% confidence interval from 38.1 to 54.4 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -12.7 with a 95% confidence interval from -31.7 to 11.7.

#### Iosco County^{6,10}

- Rate : The incidence rate is 45.2 # with a 95% confidence interval from 35.9 to 56.7 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 2.4 with a 95% confidence interval from -32.9 to 56.2.

#### Lapeer County^{6,10}

- Rate : The incidence rate is 45.1 # with a 95% confidence interval from 39.2 to 51.6 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 2.7 with a 95% confidence interval from -13.5 to 21.9.

#### Saginaw County^{6,10}

- Rate : The incidence rate is 44.9 # with a 95% confidence interval from 41.2 to 48.9 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -14.7 with a 95% confidence interval from -27.9 to 1.0.

#### Huron County^{6,10}

- Rate : The incidence rate is 44.9 # with a 95% confidence interval from 37.1 to 54.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -11.1 with a 95% confidence interval from -21.6 to 0.7.

#### Shiawassee County^{6,10}

- Rate : The incidence rate is 44.6 # with a 95% confidence interval from 38.3 to 51.7 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -8.5 with a 95% confidence interval from -27.0 to 14.6.

#### Kalkaska County^{6,10}

- Rate : The incidence rate is 44.6 # with a 95% confidence interval from 32.7 to 59.6 and average annual cases over .

#### Macomb County^{7,8}

- Rate : The incidence rate is 43.6 with a 95% confidence interval from 41.8 to 45.5 and 432 average annual cases over 2008-2012.
- Recent Trend : The trend is falling because the trend is -2.0 with a 95% confidence interval from -2.4 to -1.6.

#### Wexford County^{6,10}

- Rate : The incidence rate is 43.2 # with a 95% confidence interval from 34.4 to 53.7 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 15.2 with a 95% confidence interval from -17.1 to 60.0.

#### Grand Traverse County^{6,10}

- Rate : The incidence rate is 43.0 # with a 95% confidence interval from 37.5 to 49.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -4.1 with a 95% confidence interval from -18.4 to 12.7.

#### Mackinac County^{6,10}

- Rate : The incidence rate is 42.7 # with a 95% confidence interval from 30.3 to 59.8 and average annual cases over .

#### Baraga County^{6,10}

- Rate : The incidence rate is 42.0 # with a 95% confidence interval from 26.3 to 64.3 and average annual cases over .

#### Genesee County^{6,10}

- Rate : The incidence rate is 41.9 # with a 95% confidence interval from 39.3 to 44.6 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -5.2 with a 95% confidence interval from -13.8 to 4.4.

#### Montmorency County^{6,10}

- Rate : The incidence rate is 41.6 # with a 95% confidence interval from 28.9 to 60.2 and average annual cases over .

#### Ingham County^{6,10}

- Rate : The incidence rate is 41.6 # with a 95% confidence interval from 38.1 to 45.4 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.8 with a 95% confidence interval from -13.2 to 8.9.

#### Charlevoix County^{6,10}

- Rate : The incidence rate is 41.6 # with a 95% confidence interval from 32.7 to 52.5 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.0 with a 95% confidence interval from -29.3 to 35.8.

#### Manistee County^{6,10}

- Rate : The incidence rate is 41.3 # with a 95% confidence interval from 32.4 to 52.2 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 4.0 with a 95% confidence interval from -24.2 to 42.6.

#### Sanilac County^{6,10}

- Rate : The incidence rate is 41.2 # with a 95% confidence interval from 34.0 to 49.6 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -6.7 with a 95% confidence interval from -16.7 to 4.6.

#### Bay County^{6,10}

- Rate : The incidence rate is 41.0 # with a 95% confidence interval from 36.3 to 46.2 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -7.1 with a 95% confidence interval from -17.9 to 5.2.

#### Van Buren County^{6,10}

- Rate : The incidence rate is 40.5 # with a 95% confidence interval from 34.6 to 47.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.7 with a 95% confidence interval from -11.9 to 7.5.

#### Lenawee County^{6,10}

- Rate : The incidence rate is 40.5 # with a 95% confidence interval from 35.5 to 45.9 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 3.7 with a 95% confidence interval from -14.0 to 24.9.

#### Roscommon County^{6,10}

- Rate : The incidence rate is 40.1 # with a 95% confidence interval from 32.1 to 50.3 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -7.6 with a 95% confidence interval from -45.0 to 55.1.

#### Ionia County^{6,10}

- Rate : The incidence rate is 40.0 # with a 95% confidence interval from 33.2 to 47.8 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -16.2 with a 95% confidence interval from -28.7 to -1.6.

#### Gladwin County^{6,10}

- Rate : The incidence rate is 40.0 # with a 95% confidence interval from 31.5 to 50.4 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -12.0 with a 95% confidence interval from -37.0 to 22.9.

#### Oakland County^{7,8}

- Rate : The incidence rate is 39.9 with a 95% confidence interval from 38.4 to 41.4 and 550 average annual cases over 2008-2012.
- Recent Trend : The trend is falling because the trend is -2.1 with a 95% confidence interval from -2.5 to -1.7.

#### St. Joseph County^{6,10}

- Rate : The incidence rate is 39.7 # with a 95% confidence interval from 33.5 to 46.8 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.4 with a 95% confidence interval from -7.0 to 2.4.

#### Muskegon County^{6,10}

- Rate : The incidence rate is 39.4 # with a 95% confidence interval from 35.5 to 43.7 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -6.4 with a 95% confidence interval from -13.4 to 1.1.

#### Livingston County^{6,10}

- Rate : The incidence rate is 38.9 # with a 95% confidence interval from 34.9 to 43.2 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.4 with a 95% confidence interval from -17.4 to 15.3.

#### Benzie County^{6,10}

- Rate : The incidence rate is 38.9 # with a 95% confidence interval from 28.6 to 52.1 and average annual cases over .

#### Oceana County^{6,10}

- Rate : The incidence rate is 38.9 # with a 95% confidence interval from 30.1 to 49.7 and average annual cases over .

#### Branch County^{6,10}

- Rate : The incidence rate is 38.7 # with a 95% confidence interval from 31.6 to 47.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -12.5 with a 95% confidence interval from -32.8 to 13.8.

#### Washtenaw County^{6,10}

- Rate : The incidence rate is 38.5 # with a 95% confidence interval from 35.4 to 41.8 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -12.0 with a 95% confidence interval from -14.6 to -9.3.

#### Presque Isle County^{6,10}

- Rate : The incidence rate is 38.0 # with a 95% confidence interval from 27.6 to 52.4 and average annual cases over .

#### Houghton County^{6,10}

- Rate : The incidence rate is 37.9 # with a 95% confidence interval from 29.9 to 47.5 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -0.3 with a 95% confidence interval from -16.5 to 19.0.

#### Clare County^{6,10}

- Rate : The incidence rate is 37.7 # with a 95% confidence interval from 30.0 to 47.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.0 with a 95% confidence interval from -32.9 to 43.0.

#### Jackson County^{6,10}

- Rate : The incidence rate is 37.7 # with a 95% confidence interval from 33.8 to 41.9 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -4.1 with a 95% confidence interval from -16.4 to 10.0.

#### Kent County^{6,10}

- Rate : The incidence rate is 37.5 # with a 95% confidence interval from 35.3 to 39.8 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -5.7 with a 95% confidence interval from -12.2 to 1.3.

#### Kalamazoo County^{6,10}

- Rate : The incidence rate is 37.5 # with a 95% confidence interval from 34.1 to 41.0 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -4.2 with a 95% confidence interval from -10.4 to 2.5.

#### Otsego County^{6,10}

- Rate : The incidence rate is 37.1 # with a 95% confidence interval from 28.3 to 47.9 and average annual cases over .

#### Cheboygan County^{6,10}

- Rate : The incidence rate is 37.0 # with a 95% confidence interval from 28.4 to 47.8 and average annual cases over .

#### Emmet County^{6,10}

- Rate : The incidence rate is 36.6 # with a 95% confidence interval from 29.1 to 45.6 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 9.0 with a 95% confidence interval from -2.5 to 21.9.

#### Calhoun County^{6,10}

- Rate : The incidence rate is 36.4 # with a 95% confidence interval from 32.3 to 40.9 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -11.0 with a 95% confidence interval from -27.5 to 9.2.

#### Alcona County^{6,10}

- Rate : The incidence rate is 35.8 # with a 95% confidence interval from 25.2 to 51.9 and average annual cases over .

#### Ogemaw County^{6,10}

- Rate : The incidence rate is 35.6 # with a 95% confidence interval from 26.8 to 46.8 and average annual cases over .

#### Ottawa County^{6,10}

- Rate : The incidence rate is 35.5 # with a 95% confidence interval from 32.3 to 39.0 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.4 with a 95% confidence interval from -14.3 to 11.2.

#### Newaygo County^{6,10}

- Rate : The incidence rate is 35.5 # with a 95% confidence interval from 29.0 to 43.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 10.5 with a 95% confidence interval from -30.8 to 76.3.

#### Luce County^{6,10}

- Rate : The incidence rate is 35.3 # with a 95% confidence interval from 20.1 to 59.2 and average annual cases over .

#### Midland County^{6,10}

- Rate : The incidence rate is 34.9 # with a 95% confidence interval from 29.8 to 40.6 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -3.0 with a 95% confidence interval from -26.9 to 28.7.

#### Montcalm County^{6,10}

- Rate : The incidence rate is 34.6 # with a 95% confidence interval from 28.8 to 41.3 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -11.1 with a 95% confidence interval from -19.2 to -2.3.

#### Monroe County^{6,10}

- Rate : The incidence rate is 34.6 # with a 95% confidence interval from 30.7 to 38.9 and average annual cases over .
- Recent Trend : The trend is falling because the trend is -10.8 with a 95% confidence interval from -16.9 to -4.3.

#### Hillsdale County^{6,10}

- Rate : The incidence rate is 33.8 # with a 95% confidence interval from 27.3 to 41.5 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -4.1 with a 95% confidence interval from -31.9 to 35.1.

#### Delta County^{6,10}

- Rate : The incidence rate is 33.0 # with a 95% confidence interval from 26.2 to 41.1 and average annual cases over .
- Recent Trend : The trend is rising because the trend is 12.5 with a 95% confidence interval from 2.7 to 23.1.

#### Allegan County^{6,10}

- Rate : The incidence rate is 32.8 # with a 95% confidence interval from 28.4 to 37.6 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -2.8 with a 95% confidence interval from -15.0 to 11.1.

#### Gogebic County^{6,10}

- Rate : The incidence rate is 32.4 # with a 95% confidence interval from 23.0 to 45.1 and average annual cases over .

#### Antrim County^{6,10}

- Rate : The incidence rate is 32.3 # with a 95% confidence interval from 24.6 to 42.1 and average annual cases over .

#### Alger County^{6,10}

- Rate : The incidence rate is 32.3 # with a 95% confidence interval from 20.1 to 50.6 and average annual cases over .

#### Marquette County^{6,10}

- Rate : The incidence rate is 32.0 # with a 95% confidence interval from 26.6 to 38.3 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -9.1 with a 95% confidence interval from -37.1 to 31.4.

#### Menominee County^{6,10}

- Rate : The incidence rate is 31.0 # with a 95% confidence interval from 23.6 to 40.5 and average annual cases over .

#### Dickinson County^{6,10}

- Rate : The incidence rate is 31.0 # with a 95% confidence interval from 23.4 to 40.5 and average annual cases over .

#### Leelanau County^{6,10}

- Rate : The incidence rate is 30.7 # with a 95% confidence interval from 22.5 to 41.4 and average annual cases over .

#### Eaton County^{6,10}

- Rate : The incidence rate is 30.3 # with a 95% confidence interval from 26.0 to 35.0 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -13.8 with a 95% confidence interval from -32.9 to 10.8.

#### Mecosta County^{6,10}

- Rate : The incidence rate is 30.2 # with a 95% confidence interval from 23.8 to 38.0 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -11.9 with a 95% confidence interval from -41.9 to 33.6.

#### Cass County^{6,10}

- Rate : The incidence rate is 29.2 # with a 95% confidence interval from 23.6 to 35.8 and average annual cases over .
- Recent Trend : The trend is stable because the trend is 7.3 with a 95% confidence interval from -28.3 to 60.6.

#### Crawford County^{6,10}

- Rate : The incidence rate is 28.9 # with a 95% confidence interval from 19.8 to 41.7 and average annual cases over .

#### Chippewa County^{6,10}

- Rate : The incidence rate is 28.7 # with a 95% confidence interval from 22.2 to 36.6 and average annual cases over .

#### Mason County^{6,10}

- Rate : The incidence rate is 28.2 # with a 95% confidence interval from 21.2 to 37.0 and average annual cases over .

#### Missaukee County^{6,10}

- Rate : The incidence rate is 28.0 # with a 95% confidence interval from 18.5 to 41.1 and average annual cases over .

#### Arenac County^{6,10}

- Rate : The incidence rate is 27.4 # with a 95% confidence interval from 18.9 to 39.2 and average annual cases over .

#### Lake County^{6,10}

- Rate : The incidence rate is 27.2 # with a 95% confidence interval from 17.4 to 42.0 and average annual cases over .

#### Iron County^{6,10}

- Rate : The incidence rate is 24.1 # with a 95% confidence interval from 16.2 to 36.5 and average annual cases over .

#### Clinton County^{6,10}

- Rate : The incidence rate is 22.1 # with a 95% confidence interval from 17.8 to 27.1 and average annual cases over .
- Recent Trend : The trend is stable because the trend is -10.5 with a 95% confidence interval from -29.9 to 14.2.

#### Barry County^{6,10}

- Rate : The incidence rate is 20.5 # with a 95% confidence interval from 16.0 to 26.0 and average annual cases over .

**Keweenaw County**

^{6,10}- Rate : * Data has been suppressed to ensure confidentiality and stability of rate estimates. Counts are suppressed if fewer than 16 cases were reported in a specific area-sex-race category. If an average count of 3 is shown, the total number of cases for the time period is 16 or more which exceeds suppression threshold (but is rounded to 3).

**Notes:**

Created by statecancerprofiles.cancer.gov on 02/05/2016 5:14 pm.

Data for the United States does not include data from Nevada.

State Cancer Registries may provide more current or more local data.

† Incidence rates (cases per 100,000 population per year) are age-adjusted to the 2000 US standard population (19 age groups: <1, 1-4, 5-9, ... , 80-84, 85+). Rates are for invasive cancer only (except for bladder cancer which is invasive and in situ) or unless otherwise specified. Rates calculated using SEER*Stat. Population counts for denominators are based on Census populations as modified by NCI. The 1969-2013 US Population Data File is used for SEER and NPCR incidence rates.

‡ Incidence data come from different sources. Due to different years of data availability, most of the trends are AAPCs based on APCs but some are APCs calculated in SEER*Stat. Please refer to the source for each area for additional information.

§ The total count for the US (SEER+NPCR) may differ from the summation of the individual states reported in this table. The total uses data from the CDC's National Program of Cancer Registries Cancer Surveillance System (NPCR-CSS) January 2015 data submission for the following states: California, Kentucky, Louisiana, and New Jersey but data for those states when shown individually are sourced from the SEER November 2014 submission.

# Data do not include cases diagnosed in other states for those states in which the data exchange agreement specifically prohibits the release of data to third parties.

* Data has been suppressed to ensure confidentiality and stability of rate estimates. Counts are suppressed if fewer than 16 cases were reported in a specific area-sex-race category. If an average count of 3 is shown, the total number of cases for the time period is 16 or more which exceeds suppression threshold (but is rounded to 3).

^{1}Source: CDC's National Program of Cancer Registries Cancer Surveillance System (NPCR-CSS) November 2014 data submission and SEER November 2014 submission.

^{5}Source: State Cancer Registry and the CDC's National Program of Cancer Registries Cancer Surveillance System (NPCR-CSS) November 2014 data submission. State rates include rates from metropolitan areas funded by SEER.

^{6}Source: State Cancer Registry and the CDC's National Program of Cancer Registries Cancer Surveillance System (NPCR-CSS) November 2014 data submission. State rates include rates from metropolitan areas funded by SEER.

^{7}Source: SEER November 2014 submission.

^{8}Source: Incidence data provided by the SEER Program. AAPCs are calculated by the Joinpoint Regression Program and are based on APCs. Data are age-adjusted to the 2000 US standard population (19 age groups: <1, 1-4, 5-9, ... , 80-84,85+). Rates are for invasive cancer only (except for bladder cancer which is invasive and in situ) or unless otherwise specified. Population counts for denominators are based on Census populations as modifed by NCI. The 1969-2013 US Population Data File is used with SEER November 2014 data.

^{10}Source: Incidence data provided by the National Program of Cancer Registries (NPCR). EAPCs calculated by the National Cancer Institute using SEER*Stat. Rates are age-adjusted to the 2000 US standard population (19 age groups: <1, 1-4, 5-9, ... , 80-84,85+). Rates are for invasive cancer only (except for bladder cancer which is invasive and in situ) or unless otherwise specified. Population counts for denominators are based on Census populations as modified by NCI. The 1969-2013 US Population Data File is used with NPCR November 2014 data.

Please note that the data comes from different sources. Due to different years of data availablility, most of the trends are AAPCs based on APCs but some are APCs calculated in SEER*Stat. Please refer to the source for each graph for additional information.

Interpret Rankings provides insight into interpreting cancer incidence statistics. When the population size for a denominator is small, the rates may be unstable. A rate is unstable when a small change in the numerator (e.g., only one or two additional cases) has a dramatic effect on the calculated rate.