This section examines certain historical trends that affect the County's needs for jail beds, including the County's growing population, criminal caseload, jail bookings, and the jail's average daily population.

As a County's population grows, the demands on its criminal justice system also grow. More crime, more arrests, more criminal case filings, and an increasing jail population can all be attributed, at least in part, to a County's growing population.

The population of Johnson County has grown steadily since 1970, and is projected to continue to increase through the year 2020.

From 1970 to 1980, the County's population increased by more than 13 percent, from 72,127 in 1970, to 81,717 in 1980. From 1980 to 1990, the County's population increased by almost 18 percent to 96,119.

From 1990 to 1996, Johnson County had the fourth largest increase in population among Iowa counties (behind Polk, Linn, and Scott Counties). During this period, Johnson County was one of 12 Iowa counties with a population growth rate in excess of five percent (i.e., 5.7 percent).

Current projections estimate that the County's population will reach 108,140 by the year 2000 (representing a 13 percent increase from 1990). The County's population is projected to reach 121,790 by 2010 (a 13 percent increase), and 136,550 by 2020 (a 12 percent increase).

The graph and table on page 11 show the historical population of Johnson County from 1970 through 1990, and the County's projected population from the year 2000 through 2020.

The number and type of criminal case filings can also provide important information regarding trends in the County's criminal justice system that may influence jail planning.

Overall, the County's criminal caseload has increased steadily and significantly since 1982. According to information from the County Attorney, the number of criminal case filings in Johnson County has quadrupled during this period, from 1,146 cases in 1982 to 4,640 cases in 1998. This represents an average rate of growth of almost ten percent a year during this period.

The County has experienced significant growth in both OWI cases and non-OWI cases. From 1982 to 1998, the number of OWI cases increased by 196 percent, and non-OWI cases increased by 362 percent. From 1982 through 1998, OWI cases represented approximately one-third (i.e., 32 percent) of the County's criminal caseload. This percentage has been slowly declining, however, with OWI cases representing approximately one-fourth of the County's criminal caseload in 1998.

The graph and table on page 12 provide a breakdown of the County's criminal caseload for OWI and non-OWI cases in Johnson County from 1982 through 1998.

The number of bookings is an important indicator of the quantity and frequency of prisoners being brought into a jail facility. The number of admissions also has an impact on the size of the overall jail population, and provides an insight into the demands placed on the facility's intake and release area, and the staff involved with the processing of inmates into (and out of) the facility.

The number of bookings at the Johnson County Jail has increased steadily and significantly since FY 1982. According to information from the Sheriff's Department, the number of bookings has more than quadrupled during this period, from 1,580 bookings in FY 1982 to 7,087 bookings in FY 1998. This represents an average rate of growth of almost ten percent a year during this period.

Although the number of bookings tend to be greater on certain days of the week, the average number of bookings per day has increased from 4.3 per day in FY 1982 to 19.4 per day in FY 1999.

During the first four months of FY 2000 (July - October, 1999), there have been a total of 2,355 bookings, which is consistent with the pace set in FY 1999.

The graph and table on page 13 show the total annual bookings from FY 1982 through FY 1999, and the trend line through this data.

Of all statistical indicators, past jail population trends generally provide the best information with regard to the County's utilization of jail beds. While crime and arrest trends, criminal caseload trends, and County population trends all have an impact, to some extent, on the County's criminal justice system, it is clear that the facility's average daily population data provides the most direct information regarding trends in the County's actual utilization of jail beds.

The average daily population (ADP) of a jail facility is one of the single most important statistical indicators in assessing the need for jail beds. The ADP is a calculation used to establish the average inmate population at any given point in time. Obviously, in reality, the actual number of inmates in a facility can fluctuate, above or below the average, depending on the actual number of inmate admissions and releases, which occur on a daily basis.

The average daily population at the Johnson County Jail has increased steadily and significantly since 1981. According to information from the Sheriff's Department, the average daily population at the jail has more than tripled during this period, from an ADP of 25.4 inmates in 1981 to an ADP of 94.1 inmates during the first three-quarters of 1999. This represents an average rate of growth of over eight percent a year during this period.

The graph and table on page 14 show the average daily population for each year from 1981 through 1999, and the trend line through this data.

A more detailed assessment was made of the County's most recent inmate population trends by examining the jail's ADP for each month from January of 1993 to present. The ADP has steadily increased from an average of 51.6 inmates in 1993 to an average of 94.1 inmates during the first three-quarters of 1999. This represents an average rate of growth of almost 1.3 percent a month during this period. During this period, the average daily population ranged from a low of 33.9 inmates in May of 1993, to a high of 99.8 inmates in April of 1999.

The graph and table on page 15 show the average daily population each month from January of 1993 through September of 1999, and the trend line through this data. The graph also shows how the ADP compares with the total number of beds at the jail.

As previously mentioned, the actual number of inmates in the Johnson County Jail can fluctuate — above or below the average — depending on the number of inmate admissions and releases.

A closer assessment was also made of the highest and lowest inmate population at the Johnson County Jail for each month from January of 1993 to present. During this period, the jail population ranged from a one-day low of 21 inmates on May 18, 1993, to a one-day high of 127 inmates on April 24, 1999.

Since 1993, the high population (or "peak" population) at the jail each month has averaged approximately 25 percent over the ADP for that month.

The graph and table on page 16 show the high and low population each month from January of 1993 through September of 1999, and compares this data to the ADP each month. The graph also shows how this data compares with the total number of beds at the jail.

Year	County Population	10 - Year Increase
1970	72,127
1980	81,717	13.3%
1990	96,119	17.6%
2000	108,140	12.5%
2010	121,790	12.6%
2020	136,550	12.1%

Year	Non-OWI	OWI	Total
1982	750	396	1,146
1983	725	582	1,307
1984	842	343	1,185
1985	974	454	1,428
1986	1,007	546	1,553
1987	1,232	646	1,878
1988	1,628	976	2,604
1989	2,008	888	2,896
1990	1,779	1,013	2,792
1991	2,171	1,035	3,206
1992	2,224	1,081	3,305
1993	2,337	1,156	3,493
1994	2,251	1,013	3,264
1995	2,652	903	3,555
1996	2,834	1,036	3,870
1997	2,880	1,044	3,924
1998	3,467	1,173	4,640

Fiscal Year	Total Bookings	Average Daily Bookings
1982	1,580	4.3
1983	2,486	6.8
1984	2,517	6.9
1985	2,524	6.9
1986	2,968	8.1
1987	3,253	8.9
1988	3,557	9.7
1989	3,860	10.6
1990	4,624	12.7
1991	5,007	13.7
1992	5,040*	13.8*
1993	5,072	13.9
1994	5,223	14.3
1995	5,273	14.4
1996	5,537	15.1
1997	5,950	16.3
1998	6,748	18.5
1999	7,087	19.4

Year	ADP
1981	25.4
1982	27.2
1983	30.9
1984	28.3
1985	36.8
1986	40.5
1987	45.0
1988	45.9
1989	58.8
1990	57.5
1991	61.2
1992	58.7
1993	51.6
1994	61.1
1995	64.3
1996	66.9
1997	75.0
1998	83.8
1999 (Jan. - Oct.)	94.1

Month	1993		1994		1995		1996		1997		1998		1999
	High	Low	High	Low	High	Low	High	Low	High	Low	High	Low	High	Low
January	71	46	69	44	74	44	89	59	97	59	99	65	111	73
February	73	37	74	48	74	49	96	71	90	63	110	51	109	67
March	62	36	69	45	78	54	88	53	82	56	100	65	110	80
April	55	30	76	47	79	48	79	51	92	61	101	70	127	86
May	54	21	79	51	76	45	82	53	86	62	99	56	114	83
June	61	30	70	52	74	48	88	57	75	55	100	72	112	81
July	80	50	72	50	72	48	75	58	84	56	96	70	111	86
August	75	47	71	51	91	55	74	54	81	55	98	58	110	79
September	71	40	95	56	97	66	78	50	102	69	115	68	109	77
October	85	48	89	57	97	55	85	46	109	70	107	59	119	79
November	75	46	75	50	74	56	87	57	105	58	116	72
December	56	32	69	42	83	45	82	52	90	54	124	74