Fabio Braggion and Steven Ongena have a post at Vox which looks at corporate leverage and firm-bank relationships in the UK from 1895 to 2009. They document an increase in corporate leverage from c.1970 and a simultaneous increase in firms having multiple relationships with banks. Braggion and Ongena argue that the increase in leverage can be traced to the deregulation of the UK banking system in the early 1970s and the breaking up of the banking cartel. Their working paper is available here.
My colleague and former PhD student Gareth Campbell has created a website about the British Railway Mania - click here . This episode has been described by the Economist as probably the greatest bubble in human history. Gareth's website provides background on the Mania and posits some explanations for the 'bubble'. In his explanation of why the bubble happened, Gareth places a lot of emphasis on investor myopia regarding future dividends and uncalled capital. His study of investors during the episode does not support the view that this episode was fuelled by naive and irrational investors.