The technology sector is set to receive the most capital in 15 years, an inflow that would represent about 25% of assets under management, according to Bank of America Merrill Lynch data. This measure has not exceeded 17% since the dot-com bubble of the early 2000s. Investors have shown confidence in and increased appetite for tech stocks. The Nasdaq 100 closed above its 50-day moving average for 113 consecutive seasons, marking the longest streak since 2011, and the seventh longest on record since 1985.

This year, out of all the Internet ETFs, the First Trust Dow Jones Internet Index Fund (FDN) has increased by 19%, PowerShares Nasdaq Internet Portfolio (PNQI) is up by more than 25%, and the Technology Select Sector SPDR Exchange Traded Fund (XLK) has gained 15% to become the best performer among the S&P 500’s 11 sectors. These gains can be compared with the S&P 500 which only rose by 6.7%. Additionally, the five biggest holdings of the First Trust and PowerShare funds have all enjoyed double digit gains in share prices. Among these, Amazon (AMZN), Facebook Inc. (FB), and Netflix Inc. (NFLX) are up by about 30% and Google’s parent company Alphabet Inc. (GOOG) has gained 27%.

The market cap of some of these tech titans is even greater than the economic output of many large metropolitan cities – Alphabet’s market cap is larger than the GDP of Chicago, Amazon’s is larger than the GDP of Washington D.C., and at $1.45 trillion the combined market capitalization of Alphabet and Apple is larger than the combine market capitalization of all Eurozone and Japanese banks.

While tech stocks have been surging and investor faith has been high, there are questions and concerns about another bubble. Moreover, amidst this renewed confidence, market breadth has been narrowing, as buyers have continued to focus more of their attention to a select few and shrinking group of rising stocks. The tech sector is the largest sector in the S&P 500, and it comprised 20.8% at the end of 2016 compared with 34.5% during the peak of the dot-com bubble. While it is good news that the market’s biggest sector has made the biggest gains, which means a strong performance by equities overall, it leaves room for vulnerabilities if sentiment goes sour in the future.

Analysts have, however, also highlighted differences between this year and the year 2000 – companies are more established now and major players have stronger profits. According to BAML strategists, while the price to earnings (P/E) ratio in the global tech sector was 50 in March 2000, it is 18 currently, far below the level during the dot-com bubble. Ultimately, in 2017 tech earnings per share numbers are strengthening, and are forecasted to increase by 16% which argues against the case for excess valuation.

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