GDP dropped 0.1% not 3%. Could be the annualization by he BEA and each quarter is on a Seqsonally Adjusted Annualized Rate (SAAR). This allows for every quarter to be compared to another quarter taking seasonality into account. This is similar to the Housing Starts numbers. For example December starts were reported at 954,000. There were not 954,000 starts in December there were only 61,500 but the seasonal factor applied gets it to 954,000 seasonally adjusted annualized rate. The GDP data is also SAAR. That could account for the difference but I’m guessing a bit.
The comparison could also have a difference between cash and accrual based accounting. Also guessing...
GDP did drop more that 3%...third quarter gdp growth rate was 3.1%...fourth quarter was -.1%. That is a huge drop...please go study gdp numbers by quarters for the past thirty years or so and you will see what I am talking about.
Yes, these are seasonally adjusted rates, most of the stats you see reported will be seasonally adjusted...otherwise question their relevance.