Our operating income increased 154% in the first quarter of 2021 versus the first quarter of 2020, which was before the impact of the pandemic.
The 30% year-over-year increase in U.S. housing permits and associated housing starts shows the strength in residential construction activity that benefited our downstream building products business.
For the first quarter of 2021, we reported net income of $242 million or $1.87 per share compared to net income of $145 million for the first quarter 2020, which included a $62 million tax benefit from the CARES Act.
These results are inclusive of the previously mentioned severe winter storm impact of approximately $100 million or $0.61 per share in the first quarter.
The $97 million first quarter year-over-year increased net income is a result of higher sales prices and integrated margins for polyethylene and PVC and higher earnings resulting from the strong demand in our downstream building products business.
While we work quickly to get our facilities back online, our estimates for a loss margin from sales and repair expense are approximately $120 million.
We incurred approximately $100 million in the first quarter of 2021 results or approximately $0.61 per share, with the remaining $20 million falling into the second quarter.
Of this estimated first quarter impact of $100 million, approximately 75% was related to our Vinyls segment, with the balance affecting our Olefins segment.
First quarter 2021 net income increased by $129 million from fourth quarter 2020 net income of $113 million.
Our utilization of the FIFO method of accounting resulted in a favorable pre-tax impact of approximately $55 million or $0.33 per share compared to what earnings would have been reported under the LIFO method.
For the first quarter of 2021, Vinyls operating income of $200 million increased $127 million from the prior year period, primarily as a result of higher sales prices and margins for PVC resin and higher sales prices and margins in our downstream building products business.
For the first quarter of 2021, Vinyls operating income increased $34 million from fourth quarter of 2020, primarily the result of higher sales for PVC resin and higher volumes in our downstream building products business.
Our first quarter 2021 operating income of $180 million increased $118 million from the first quarter 2020, driven by strong pricing and improved demand, offset by lower sales volumes resulting from the severe winter storm.
For the first quarter 2021, Olefins operating income increased $158 million from fourth quarter of 2020, primarily due to higher sales prices and margins as well as increased sales volumes, partially offset by higher feedstock and fuel cost.
We generated $265 million in cash flows from operations in the first quarter 2021, resulting in total cash and cash equivalents of $1.4 billion.
First quarter 2021 capital expenditures were $141 million.
We maintain a long-dated debt maturity profile with a weighted average debt maturity of 14 years, anchoring our investment-grade balance sheet.
We expect our effective tax rate for the full year of 2021 to be approximately 23% and a cash tax rate of approximately 19%.
As we stated in our last call, we forecast our capital expenditures for the year to be between $700 million and $800 million.
This turnaround and associated outage is expected to last approximately 60 days.
This product is available under the brand name GreenVin, which has a reduced CO2 impact of more than 30% compared to conventional caustic soda.

Summary:
For the first quarter of 2021, we reported net income of $242 million or $1.87 per share compared to net income of $145 million for the first quarter 2020, which included a $62 million tax benefit from the CARES Act.