Despite regulatory pressure to reign it in, the world’s biggest money market fund –overseen by China’s Ant Financial Services Group– gained an additional 114 million investors last year, bringing its total assets under management to $168 billion. This according to an article in The Wall Street Journal.

The Tianhong Yu’e Bao fund, launched in 2013, allows users of the firm’s highly popular mobile-payments network Alipay to invest their spare cash for short periods before spending it online. Alipay users can make payments with their mobile phones for a vast array of products and services.

“Many investors in the fund treat it like an online checking account, depositing money at all hours of the day and withdrawing funds whenever they need to spend money,” the article reports, adding that the fund’s investor base grew by 24% last year despite a 28% decrease in assets under management.

When the fund grew to 1.69 trillion yuan last March, the article reports that regulators became worried about its potential risk to China’s financial system: “Its manager has taken a series of steps to limit inflows and reduce its holdings of hard-to-sell assets, dropping its yields in the process.” The article  notes that the fund’s annualized yield was recently 2.379%, still well above short-term Chinese bank deposit rates.

A financial affiliate of Alibaba Group Holding Ltd., Ant Financial is “the world’s most valuable financial-technology startup,” according to the article.