This paper investigates the internal versus external financing decisions among 1900 early stage privately held UK firms in 1996-1997. The authors study the factors that affect rejection rates in applications for outside finance among the different types of investors, taking into account the non-randomness in a firms decision to seek outside finance.
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http://papers.ssrn.com/sol3/Delivery.cfm/SSRN_ID663841_code75390.pdf?abstractid=663841&mirid=1