A nice paper about the macro impact of VC - that it's social return is greater than that of either R&D or business, because it has a greater effect on innovative and absorptive capacity:
"...According to a study carried out by DRI-WEFA1 on US VC-funded companies over the period 1970- 2000, �venture capital-backed companies had approximately twice the sales, paid almost three times the federal taxes, generated almost twice the exports, and invested almost three times as much in R&D as the average non-venture capital-backed public company, per each $1,000 of assets�.