The US stock market has risen too fast in the past week, and CTA has not had a chance to get on board yet. Goldman Sachs' improved CTA estimation core data (as of April 13, 2026) shows that the Goldman Sachs model: Last week, CTA bought about $19 billion worth of US stocks, and currently CTA still holds about $30 billion in short positions on the S&P 500. This week's expected buying will flatten these short positions and flip to long. Expected buying for the next week (all scenarios are buying, and the scale has reached a historical second highest/record level): 1) Flat scenario: US stock purchases of approximately $43.5 billion (including approximately $34 billion for the S&P 500 and related ETFs) 2) Upward scenario: US stock purchases of approximately $43.6 billion (S&P 500 concentration of approximately $34 billion) 3) Downward scenario: US stock purchases of approximately $29.9 billion (S&P 500 still net purchases) Future buying forecast (also biased towards bullish scenarios): Flat: US stocks buy approximately $61 billion Rising: US stocks buy about $66 billion Decline: US stocks sold only about $761 million (almost negligible, S&P 500 still maintains net buying) Goldman Sachs' "improvement" this time is mainly based on the latest price trend. After the recent market rebound from the pullback caused by events such as the Iran conflict, CTA's momentum signals have all turned positive (short-term threshold>6713, medium-term>6734, long-term>6400), and the current SPX is around 679-680, which has triggered large-scale buying signals. All momentum thresholds have turned positive, resulting in a significant reduction or even disappearance of potential selling scenarios, and a shift towards buying across all scenarios. This is in stark contrast to the situation where CTA may still sell net during some time periods in early March and April. What is CTA? CTA is a quantitative/systematic fund that adopts a momentum based strategy and primarily trades through futures markets, including stock index futures such as S&P 500 E-mini. They do not rely on fundamentals, but automatically increase or decrease positions based on price breakthroughs above short-term, medium-term, and long-term moving averages or momentum thresholds. Goldman Sachs' FICC&Equities Division Futures Strats Group has a proprietary model that can estimate CTA's current position and future fund flows in real-time. This is an important technical/mechanical buy or sell indicator in the market, often amplifying market trends or providing support/pressure. This batch of mechanical buying is' brainless buying '(regardless of fundamentals, only following trends), which will provide significant upward momentum for the S&P 500, especially as the market has rebounded from recent lows and is approaching historical highs. Analysts such as Neil Sethi pointed out that this batch of capital flow "shifted from net sellers in Q1 to net buyers in Q2", which may amplify any positive catalyst.