Tax Credits and Small Firm R&D Spending
研究了2004年加拿大SRED税收抵免资格规则变化对小企业研发支出的影响，发现合格企业总研发支出增加17%，且无税负企业通过退税获得更大效果。
In 2004, Canada changed the eligibility rules for its Scientific Research and Experimental Development (SRED) tax credit, which provides tax incentives for R&D conducted by small private firms. Difference-in-difference estimates show a 17 percent increase in total R&D among eligible firms. The impact was larger for firms that took the tax credits as refunds because they had no current tax liability. Contract R&D expenditures were more elastic than the R&D wage bill. The response was also greater for firms that invested in R&D capital before the policy change.