This is how strong U.S. stocks have been this year: The worst performer among the nine sector SPDR ETFs is the Utilities Select Sector SPDR (XLU) with a year-to-date gain of 14.4%.

That is not surprising as XLU is not only the highest-yielding SPDR, but also the one with lowest beta and lowest correlation to the S&P 500. The Technology Select Sector SPDR (XLK) is the next worst “offender” with a year-to-date of 18%. [A Buffett Pop for Energy ETFs]

In further testament to the strength of the 2013 rally, five SPDRs are up more than 23% and three are up more than 30%. The Consumer Discretionary Select Sector SPDR (XLY) and the Health Care Select Sector SPDR (XLV) are tussling for top honors this year.

YTD SPDR Performances