Over its 30 year development history, the balance of CSP tenants and the nature of its physical development have changed. Buildings have become higher rise as land values have increased and the need for load bearing ground floor space increased. The average size of tenant firms has increased, rising from around 35 in the 1980s to about 75 today. As a result, some of the small unit schemes developed in earlier years have been amalgamated for letting to single users. More firms have had their own, purpose-designed, premises built and a small amount of land has been released to private developers who have, speculatively, developed buildings for lease.

Number of tenant firms and employment:
Year	Firms w/out data	Firms with data	Total firms	Total employees*	Ave. employees*
1987	15	61	76	2149	35.2
1989	8	76	84	2847	37.5
1990	5	78	83	2918	37.4
1991	8	76	84	3044	40.1
1992	10	70	80	2996	42.8
1994	7	69	71	3641	52.8
1996	2	66	68	3676	55.7
2001	-	61	-	4577	75.0
* among tenants with data

In general, tenants on CSP tend to stay. The first firm came in 1973 and is still on the park today. Cambridge Consultants Limited, the major technology consultancy has grown steadily on the Park since 1979. An analysis undertaken in 1998 indicated that on average, then-current CSP companies had been on the Park for 10 years. In part this reflected the relatively slow growth during the early 1990s, but it also indicated a good deal of loyalty to the Park; reinforced by inertia and a limited range of alternative options locally.

Further - and more recent - evidence for this relative stability is provided in Table below which in a synopsis of all the companies that left CSP in the period 1997-2002. A number of conclusions and inferences may be drawn from these data: over the five year period, the evidence suggests that eight companies left CSP: an average of less than two per year among the companies leaving during this period, the average length of stay on CSP was over 13 years, and two of the departing companies had been on the Science Park since the 1970s seven of the eight departing companies moved to locations elsewhere in the Cambridge sub-region because of issues relating to evolving business models and the fact that maturing companies have changing space requirements

Companies leaving Cambridge Science Park in the period 1997-2002:
Name	Arrived	Departed	Destination	Reason for leaving
Intervet	1973	2000	Milton Keynes	Acquisition of another company and then consolidation
Ultra Violet Products	1986	1998	Trinity Hall Industrial Estate	Wanted to pay a lower level of rent
Coherent	1979	1999	Industrial Estate, Ely	Needed less space, CSP could not supply it.
Signal Processors	1985	1999	Industrial Estate, Huntingdon	Wanted less and cheaper space. Rates were an issue.
Goodfellow	1985	2001	Industrial Estate, Huntingdon	Wanted to realise the value of their CSP ground lease building.
Cambridge Cable/NTL	1994	2001	Cambridge Research Park	Nature of the business had changed
Chiroscience	1994	2000	Granta Park	They needed to consolidate 6 units into 1 and space could not be found at CSP
Peptide Therapeutics	1995	1999	Peterhouse Technology Park	Wanted the best deal on pre-letting that they could find as they were keen to keep overheads down.

Another factor influencing a company's location is the home locations of firms' staff. For any knowledge-based business, staff are likely to be the most important resource. In a tight labour market such as that of the Cambridge sub-region, this is especially true. In seeking new or additional premises, a key consideration for relocating businesses will be staff retention.

The table below summarises the results of a survey of current CSP employees in terms of their home addresses. It suggests that:

• close to 40% of employees live in the area extending north and west from Cambridge
• about 20% live to the north east or east of the City, and a similar proportion live in a broadly defined area to the south
• some 12% live in a range of disparate locations which are scattered across the broadly defined south and east of England.

Home postcodes of 1152 workers on Cambridge Science Park, 2002:
Postcode	Description	Rel. to Cambridge	Number	%age
CB4	North and north west of Cambridge	NW	322	28%
CB1	Central and south east Cambridge	SE	129	11%
CB6	Ely and area	NE	83	7%
CB5	North and east of Cambridge	NE	77	7%
CB3	West of Cambridge	W	74	6%
CB2	South of Cambridge	S	54	5%
CB7	East of Ely	NE	40	3%
SG8	Royston area	SW	38	3%
PE28	Somersham area	NW	37	3%
CB8	Newmarket area	E	32	3%
PE17	Huntindgon area (east)	NW	29	3%
PE19	St Neots?	W	25	2%
PE27	St Ives?	NW	24	2%
CB9	Haverhill	SE	20	2%
IP28	Bury St Edmunds	E	13	1%
PE1	Peterborough	NW	12	1%
Other	Elsewhere	all	142	12%
Source: Bidwell's survey of Cambridge Science Park tenants, 2002

These findings are significant in the strategic planning of the Cambridge Science Park since as companies mature they seek premises that favour locations that are likely to be least disruptive for existing staff.