Take a look at the S&P 500 over the past two months:
It is not entirely coincidental this aligns fairly well with the monetary loosening of the next phase of quantitative easing by the US Federal Reserve, which started in September:
Most of this excess capital tends to find its way pumping demand into the asset market. Right now, that demand gets centered around the large capitalization, large liquidity companies, but eventually that demand flows to parts of the economy that still offer morsels of yield.