Steve McConnell's classic "Code Complete: A Practical Handbook of Software Construction" cites a number of studies of real systems from the 1970s and 1980s with some surprising results. Some studies showed that function size inversely correlated with bug counts; as functions increased towards 200 LOC, the bug count decreased. Similar, another showed that shorter functions had more bugs per LOC and reduced comprehension for programmers new to the system. Another study showed that function complexity was correlated with bug count, but size alone wasn't.