The Consumer Discretionary Select Sector SPDR (NYSEArca: XLY), which tracks consumer discretionary names in the S&P 500 index, is already this year’s best performer among the nine sector SPDR exchange traded funds by a wide margin.

XLY and rival discretionary ETFs have also been better bets than the SPDR S&P Retail ETF (NYSEArca: XRT) and some market observers believe the divergence between big-name discretionary stocks found in XLY and smaller retailers, including those populating XRT, could be a cause for concern heading into 2016.

The Commerce Department calculated that retail sales was up 0.1% last month, compared to economists’ forecasts for an increase of 0.3%, after being unchanged in September. [America’s Less Dressed: 3 Factors Weighing On Retail ETFs]

Paul Hickey of Bespoke Investment Group “looked at the XRT, the ETF that tracks the performance of the retail group in the S&P 500. Hickey noted that since 2000, the XRT tends to outperform the broader markets in the month leading up to Thanksgiving. However, immediately following Thanksgiving, those stocks tend to fall, according to Hickey’s chart work,” reports CNBC.

“As is so often the case in markets, investing in a retail ETF over the long term may prove a jolly idea, but trying to time a play for a few weeks in late November and December is likely to put some proverbial coal in your portfolio,” adds Bloomberg.

Rich Ross of Evercore ISI told CNBC XLY has been driven higher by the likes of Amazon (NasdaqGS: AMZN), Walt Disney (NYSE: DIS) and Home Depot (NYSE: HD), “but problems in the retail space could actually drag down the broader sector heading into 2016, Ross said. The equal-weighted ETF that solely tracks retail stocks (XRT) has fallen more than 7 percent this year.”

The consumer discretionary sector is heading toward a seasonally strong period. Historically, consumer discretionary has been among the better performers during the November through April period since 1990, rising 10.7% on average, compared to the 7.1% gain for the S&P 500 index. Add to that, only two the nine sector SPDRs have taken in more new assets this year than XLY.

XLY, the largest consumer discretionary ETF by assets, includes exposure to retail firms, restaurants, media companies, apparel and luxury goods companies, automobile manufacturers and leisure industries.

Retailers make up a large portion of the underlying holdings. E-commerce and greater mobile commerce usage has also been a big game changer in the industry, especially with more consumers using online sources like Amazon, which XLY holds.

Consumer Discretionary Select Sector SPDR