The US NFIB May Small Business Index increased to 89.4, beating the estimated 88.5 and showing an improvement from April's 89. This indicates a stronger small business environment, which may have a positive impact on the overall economy and the SPY ETF. The SPY ETF is designed to track the performance of the S&P 500, and a stronger small business environment may lead to better overall economic performance, potentially benefiting the ETF.