BlackRock marks another scale milestone with the firm's S&P 500 ETF becoming the first to reach $100bn in assets under management (AUM).

Although assets have since dipped below the milestone, the iShares Core S&P 500 UCITS ETF (CSPX) remains Europe’s largest and most liquid ETF with an average daily volume (ADV) of $305m so far this year, around 4% of daily trading volume for equity ETFs collectively, according to BlackRock data.

Although the fund launched in 2010, the latest milestone comes just seven months after it reached the $75bn AUM mark.

Substantial inflows and market beta have spurred CSPX’s strong asset growth this year, with $11bn of net new assets (NNA) pouring in to make it the best-performing European ETF by flows.

The S&P 500 index, which CSPX tracks using physical replication, is up 21.2% year-to-date providing a further boost to the fund's AUM.

While CSPX’s total expense ratio (TERs) of 0.07% does not make it the cheapest S&P 500 ETF in Europe, the strategy boasts the tightest bid-ask spread of any S&P 500 ETF in Europe over the trailing month.

Higher over-the-counter (OTC) volumes for the product – which indicate increased usage as a financial instrument and greater retail participation – are also driving more frequent trading in smaller ticket sizes and have pushed volatility in spreads down to record lows.

CSPX's AUM milestone also coincided with BlackRock debuting two US equity synthetic ETFs.