Exchange traded funds tracking the retail sector are rising this week on brisk sales on Black Friday and Cyber Monday.

“This is the largest year-over-year gain…for Black Friday since the 8.3% increase we saw between 2007 and 2006,” Bill Martin for ShopperTrak said, on NPR. “Still, it’s just one day. It remains to be seen whether consumers will sustain this behavior through the holiday shopping season.”

Black Friday typically accounts for about 10% of retail holiday sales, and according to analysts, this year was strong. Black Friday shoppers that hit brick and mortar shops was up 6.6% from 2010, to 226 million, reports Heather Struck for Forbes.

SPDR S&P Retail ETF (NYSEArca: XRT) rallied over 3% on Cyber Monday, the retail industry’s direct-to-consumer online shopping day. [ETF Spotlight: Retail Sector and the Holiday Shopping Season]

“Cyber Monday figures to be a make or break day for many online retailers,” Erik Johnson, an economist, wrote on NPR. The firm is “projecting that seasonally adjusted e-commerce retail sales will increase 12.5% year-on-year in the fourth quarter, and surpass $50 billion for the first time.”