Small-cap stocks are this year’s best performers, but there are still hundreds whose valuations have declined this year, making them potentially attractive investments.

Small U.S. companies derive a greater share of sales and profits domestically than their large counterparts do, so it appears that earnings estimates haven’t yet caught up to the post-tax-cut reality. The reduction in the maximum federal income tax rate to 21% from 35% for companies certainly is a game changer, especially for smaller ones that lack the complex structures that can help large ones greatly reduce their taxable income. A company that was paying the 35% rate before the tax cut would enjoy a 22% boost to after-tax earnings, all things being equal.

We’ve screened small-cap stocks whose forward price-to-earnings ratios have declined despite big gains in the market. But, first, here’s how valuations for the three main S&P indices have changed over the past year.

All forward price-to-earnings ratios are based on weighted aggregate consensus earnings estimates for the 12 months following the date the ratio was calculated:

Index Forward P/E - Sept. 4 Forward P/E - Dec. 29 Forward P/E - Sept. 4, 2017 Total return - 2018 through Sept. 4 Total return - 12 months through Sept. 4 S&P 500 Index SPX, -0.28% 16.9 18.3 17.6 9.8% 19.2% S&P 400 Mid-Cap Index MID, -0.09% 16.8 18.3 17.4 8.5% 19.3% S&P 600 Small-Cap Index SML, -0.17% 18.3 17.9 17.3 17.8% 30.9% Source: FactSet

This is an interesting pattern. All three indices have shown significant gains over the past year, while forward P/E ratios for the large-cap S&P 500 SPX, -0.28% and the S&P 400 Mid-Cap Index MID, -0.09% have declined. The S&P 600 Small-Cap Index SML, -0.17% breaks the pattern, with better performance and a rising forward P/E.

Here’s a screen of the S&P 500 showing large-cap for stocks whose forward P/E ratios fell despite total returns of 20% or more from a year earlier.

Turning to the S&P Small-Cap 600 Index, there are some differences in the available data from those of the large-caps. Among the S&P 600, FactSet has current and year-earlier consensus forward price-to-earnings ratios available for 498 companies, because Wall Street analysts don’t cover all the small-caps.

We narrowed down those 498 small-cap companies to 39 that met these criteria:

• Stocks returned at least 20% for 12 months through Sept. 4, with dividends reinvested.

• Forward price-to-earnings ratios declined from a year earlier.

• Sales for the most recently reported quarter rose at least 20% from a year earlier.

Here’s the list of S&P 600 small-cap companies that met the criteria, sorted by how much their quarterly sales increased:

Company Ticker Industry Increase in quarterly sales Price/ earnings ratio - NTM Price/ earnings ratio - NTM - year ago Total return - Sept. 4, 2017, through Sept. 4, 2018 Penn Virginia Corp. PVAC, -3.41% Oil & Gas Production 236% 6.3 8.9 115% ProPetro Holding Corp. PUMP, +0.26% Oilfield Services/Equipment 115% 7.6 10.0 32% Shutterfly Inc. SFLY, -4.43% Internet Software/Services 112% 40.8 49.9 71% LHC Group Inc. LHCG, -1.27% Medical/Nursing Services 95% 25.3 26.4 53% First Financial Bancorp. FFBC, +0.00% Regional Banks 79% 13.7 15.4 34% Simmons First National Corp. Class A SFNC, +0.63% Regional Banks 71% 13.2 14.1 23% Cal-Maine Foods Inc. CALM, +0.00% Food: Specialty/Candy 61% 23.8 101.7 40% NMI Holdings Inc. Class A NMIH, -5.44% Property/Casualty Insurance 60% 11.7 14.1 102% Carrizo Oil & Gas Inc. CRZO, -2.60% Oil & Gas Production 59% 6.2 11.1 77% Electro Scientific Industries Inc. ESIO, -2.39% Electronic Production Equipment 52% 11.3 18.5 77% PDC Energy Inc PDCE, -0.72% Oil & Gas Production 51% 14.1 228.6 34% Patrick Industries Inc. PATK, -0.38% Building Products 49% 12.7 16.0 35% Denbury Resources Inc. DNR, -0.56% Oil & Gas Production 48% 8.1 14.1 391% Greenbrier Cos. Inc. GBX, -1.21% Trucks/Construction/Farm Machinery 44% 14.4 14.8 36% Virtus Investment Partners Inc. VRTS, -2.03% Investment Managers 41% 9.7 11.3 21% QuinStreet Inc. QNST, -4.14% Advertising/Marketing Services 37% 21.9 26.0 174% Helix Energy Solutions Group Inc. HLX, -2.52% Oilfield Services/Equipment 36% 43.5 135.1 48% Triumph Bancorp Inc. TBK, -1.39% Regional Banks 36% 15.0 15.3 53% National Bank Holdings Corp. Class A NBHC, -0.70% Regional Banks 35% 18.2 23.0 26% Chart Industries Inc. GTLS, -0.66% Industrial Machinery 34% 31.9 34.3 122% Applied Industrial Technologies Inc. AIT, +0.65% Wholesale Distributors 32% 16.5 18.6 35% Greenhill & Co. Inc. GHL, -0.55% Investment Banks/Brokers 32% 19.9 23.5 89% Callaway Golf Co. ELY, +0.52% Recreational Products 30% 23.7 28.7 67% Federal Signal Corp. FSS, +3.23% Trucks/Construction/Farm Machinery 30% 19.2 20.5 38% LGI Homes Inc. LGIH, +0.64% Homebuilding 30% 8.3 10.1 25% Newpark Resources Inc. NR, -1.48% Oilfield Services/Equipment 29% 17.8 35.3 23% Hub Group Inc. Class A HUBG, -0.50% Air Freight/Couriers 28% 19.8 21.8 30% Great Western Bancorp Inc. GWB, +0.67% Regional Banks 26% 13.5 14.1 23% National Storage Affiliates Trust NSA, +1.19% Real Estate Investment Trusts 26% 38.8 93.5 29% Diplomat Pharmacy Inc. DPLO, +0.69% Hospital/Nursing Management 26% 20.7 23.0 21% DXP Enterprises Inc. DXPE, -0.23% Industrial Machinery 24% 26.2 27.7 76% Boise Cascade Co. BCC, +2.53% Forest Products 24% 15.3 17.2 49% ServisFirst Bancshares Inc SFBS, -0.12% Regional Banks 23% 16.6 18.1 27% First Commonwealth Financial Corp. FCF, -0.71% Regional Banks 22% 15.0 15.4 35% Photronics Inc. PLAB, -2.82% Electronic Production Equipment 22% 21.5 25.5 33% Old National Bancorp ONB, -0.49% Regional Banks 22% 14.6 15.8 28% Alarm.com Holdings Inc. ALRM, +1.68% Information Technology Services 22% 48.0 52.8 27% New Media Investment Group Inc. NEWM, +0.38% Publishing: Newspapers 20% 17.4 27.9 24% Brookline Bancorp Inc. BRKL, +0.28% Savings Banks 20% 16.2 16.6 29% Souce: FactSet

You can click on the tickers for more information about each company.

Here’s a summary of analysts’ opinions about these companies:

Company Ticker Share 'buy' ratings Share neutral ratings Share 'sell' ratings Closing price - Sept. 4 Consensus price target Implied 12-month upside potential Penn Virginia Corp. PVAC, -3.41% 100% 0% 0% $82.48 $101.60 23% ProPetro Holding Corp. PUMP, +0.26% 76% 24% 0% $15.13 $21.38 41% Shutterfly Inc. SFLY, -4.43% 40% 60% 0% $77.15 $99.00 28% LHC Group Inc. LHCG, -1.27% 90% 10% 0% $100.09 $105.67 6% First Financial Bancorp. FFBC, +0.00% 33% 56% 11% $31.50 $33.63 7% Simmons First National Corp. Class A SFNC, +0.63% 20% 80% 0% $31.75 $33.75 6% Cal-Maine Foods Inc. CALM, +0.00% 20% 60% 20% $49.40 $47.40 -4% NMI Holdings Inc. Class A NMIH, -5.44% 75% 25% 0% $22.05 $25.14 14% Carrizo Oil & Gas Inc. CRZO, -2.60% 68% 32% 0% $24.23 $34.54 43% Electro Scientific Industries Inc. ESIO, -2.39% 100% 0% 0% $21.38 $32.75 53% PDC Energy Inc PDCE, -0.72% 71% 29% 0% $53.01 $74.70 41% Patrick Industries Inc. PATK, -0.38% 86% 14% 0% $65.35 $80.29 23% Denbury Resources Inc. DNR, -0.56% 10% 80% 10% $5.40 $4.73 -12% Greenbrier Cos. Inc. GBX, -1.21% 50% 50% 0% $57.85 $59.50 3% Virtus Investment Partners Inc. VRTS, -2.03% 14% 86% 0% $128.00 $144.14 13% QuinStreet Inc. QNST, -4.14% 83% 0% 17% $14.96 $17.29 16% Helix Energy Solutions Group Inc. HLX, -2.52% 87% 13% 0% $9.53 $10.67 12% Triumph Bancorp Inc. TBK, -1.39% 86% 14% 0% $43.05 $47.14 10% National Bank Holdings Corp. Class A NBHC, -0.70% 33% 67% 0% $40.05 $41.50 4% Chart Industries Inc. GTLS, -0.66% 67% 33% 0% $76.21 $89.00 17% Applied Industrial Technologies Inc. AIT, +0.65% 20% 80% 0% $76.40 $92.50 21% Greenhill & Co. Inc. GHL, -0.55% 0% 43% 57% $27.35 $22.77 -17% Callaway Golf Co. ELY, +0.52% 73% 27% 0% $22.98 $23.75 3% Federal Signal Corp. FSS, +3.23% 50% 50% 0% $25.72 $27.33 6% LGI Homes Inc. LGIH, +0.64% 33% 67% 0% $56.02 $70.20 25% Newpark Resources Inc. NR, -1.48% 86% 14% 0% $10.15 $12.43 22% Hub Group Inc. Class A HUBG, -0.50% 41% 47% 12% $50.15 $54.87 9% Great Western Bancorp Inc. GWB, +0.67% 78% 22% 0% $43.50 $49.11 13% National Storage Affiliates Trust NSA, +1.19% 33% 67% 0% $27.69 $30.63 11% Diplomat Pharmacy Inc. DPLO, +0.69% 46% 54% 0% $20.23 $25.36 25% DXP Enterprises Inc. DXPE, -0.23% 50% 50% 0% $47.01 $57.00 21% Boise Cascade Co. BCC, +2.53% 14% 86% 0% $43.45 $47.00 8% ServisFirst Bancshares Inc SFBS, -0.12% 0% 100% 0% $43.23 $44.00 2% First Commonwealth Financial Corp. FCF, -0.71% 14% 86% 0% $16.79 $18.00 7% Photronics Inc. PLAB, -2.82% 33% 67% 0% $10.65 $12.50 17% Old National Bancorp ONB, -0.49% 20% 80% 0% $20.40 $21.00 3% Alarm.com Holdings Inc. ALRM, +1.68% 75% 17% 8% $57.75 $54.09 -6% New Media Investment Group Inc. NEWM, +0.38% 50% 0% 50% $15.81 $15.50 -2% Brookline Bancorp Inc. BRKL, +0.28% 40% 60% 0% $18.10 $19.30 7% Source: FactSet