In 1895, a British government committee on prisons, chaired by Herbert Gladstone, the brother of the former prime minister, found the following probabilities of a further prison sentence (paragraph 85):

Number of Imprisonments    
Probability of Further Prison Sentence
1 30%
2 48%
3 64%
4 71%
5 79%

A century later, the Home Office found that in the first quarter of 2005, the one-year re-offending rate was:

Previous Custodial Sentence
One-Year Re-Offending Rate               
0 26.0%
1 43.0%
2 51.7%
3 57.0%
4 60.8%
5 62.7%
6-10 88.6%
11+ 78.3%
(Source:  e-mail from Home Office Statistics Department)

The data are not quite comparable, but the message is clear: Every time a person is sent to prison, he or she becomes more likely to re-offend.  Perhaps it is time we learnt this lesson.