NEW YORK ( TheStreet) -- If the potential removal of U.S. monetary stimulus wasn't enough of an excuse to sell riskier assets, this past weekend The People's Bank of China tightened liquidity measures, and on Monday, equity, commodity, and currency markets weakened to levels not seen since the beginning of the year.The first chart below is of iShares FTSE China 25 Index Fund ( FXI) over Vanguard Total World Stock Index ETF ( VT). The chart measures the relative strength of Chinese equities versus a basket of world equities. The pair has broadly sold off through much of 2013 as growth concerns, as well as structural changes to the Chinese economy, sent investors fleeing China-linked assets. That led to weakness in commodities and commodity-linked currencies. As demand for raw materials wanes in China, developing market exports decline. Tighter liquidity measures enacted by the PBOC came in the form of allowing the seven-day SHIBOR, the benchmark rate at which banks in Shanghai lend to each other, to rise toward unstable levels around 12%.