With 2015 drawing to close, it is fair to say investors have heard plenty this year about the out-performance of the growth factor relative to its quality and value counterparts.

While many academic studies have shown that U.S. value stocks and small-caps outperform over the long-term, large-cap growth stocks have taken the lead this year.

Value stocks typically trade at cheaper prices relative to fundamental measures of value, such as earnings and the book value of assets. In contrast, growth stocks tend to run at higher valuations since investors expect the rapid growth in those company measures. The $14 billion iShares S&P 500 Growth ETF (NYSEArca: IVW) has been one of the stars among growth exchange traded funds this year, posting roughly the triple the gains offered by its value counterpart and the S&P 500.

As is often the case with growth ETFs, IVW is heavily allocated to the technology and consumer discretionary sectors. Those sectors combine for nearly 51% of the ETF’s weight and it is IVW’s weight to some of this year’s high-flying NASDAQ names that have buoyed the fund, as Investor’s Business Daily notes. Apple (NasdaqGS: AAPL), Amazon (NasdaqGS: AMZN), Microsoft (NasdaqGS: MSFT) and Facebook (Nasdaq: FB) are IVW’s top four holdings, combining for nearly 17% of the ETF’s weight.

Forecasts for a rebound in value names remain murky. Weighing on the value outlook, the Federal Reserve may still hike interest rates, and energy companies, commodity producers and other firms dependent on emerging markets are vulnerable to losses if rates rise. Additionally, there is no guarantee that a reflation trade benefiting value stocks will develop, especially with the consumer price index showing tepid increases and overall inflation still stubbornly below the Fed’s 2% target.