Small caps have been underperforming large caps this year. iShares Russell 2000 ETF IWM and SPDR S&P 600 Small Cap ETF SLY are up 18.2% and 15.8%, respectively, compared with the 24.3% gain in the S&P 500 Index. This underperformance was prevalent in the past month as well, a period packed with corporate earnings releases.The reason could be consistently weak earnings witnessed by the small caps compared with their bigger counterparts.Q3 Performance: S&P 600 Versus 500The third-quarter earnings season is almost drawing to a close with 88% of the S&P 600 Index’s total participants having reported so far. Earnings are down 19.6% year over year on 1.8% higher revenues. About 62.6% members’ EPS beat estimates while 57.8% surpassed on the top line as the Earnings Trends issued on Nov 13, 2019 show.Looking at Q3 as a whole for the small-cap index, total Q3 earnings are expected to be down 19.5% from the same period last year on 3.6% higher revenues. The decline in earnings follow an 11.7% drop in earnings in Q2 and 17.3% slump in earnings in Q1, respectively.About 91% of the large-cap index S&P 500 has already reported earnings decline of 1.7% on 4.6% higher revenues. The S&P 500 Index has so far produced a blended beat ratio of 45.9%. For the third quarter, the S&P 500 is likely to be down 2% on 4.3% higher revenues.Consumer Staples — Invesco S&P SmallCap Consumer Staples ETF PSCCThe sector is likely to end the third quarter with 26.4% increase in earnings and a 17.2% revenue rise. The fund PSCC has gained 3.6% in the past month against 3.8% gain in the S&P 500 Index.Consumer Discretionary — Invesco S&P SmallCap Consumer Discretionary ETF PSCDEarnings are likely to be 12.0% higher while revenues will likely see a 10.1% uptick. However, the fund PSCD is up only 1.7% in the past month.Medical — Invesco S&P SmallCap Health Care ETF PSCHThe sector is likely to record 10% earnings growth on 2.4% higher revenues. The fund has jumped 4.7% in the past month (as of Nov 19, 2019).Construction — Invesco Dynamic Building & Construction ETF PKBThe sector is likely to record 11.3% earnings growth on 5.5% higher revenues. The fund has advanced 1.4% in the past month (as of Nov 19, 2019) (read: ETFs in Focus as US Homebuilder Sentiment Drops in November).Finance — Invesco S&P SmallCap Financials ETF PSCFEarnings are likely to be up 12.4% year over year on 7.7% higher revenues. The fund has tacked on 1.7% gains in the past month (as of Nov 19, 2019). Want key ETF info delivered straight to your inbox?Zacks' free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Invesco S&P SmallCap Consumer Staples ETF (PSCC): ETF Research Reports Invesco S&P SmallCap Health Care ETF (PSCH): ETF Research Reports Invesco Dynamic Building & Construction ETF (PKB): ETF Research Reports Invesco S&P SmallCap Consumer Discretionary ETF (PSCD): ETF Research Reports Invesco S&P SmallCap Financials ETF (PSCF): ETF Research Reports iShares Russell 2000 ETF (IWM): ETF Research Reports SPDR S&P 600 Small Cap ETF (SLY): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report