Focused on building reliable datasets, financial models, and research tools for value-minded investors. Committed to turning complex data into practical guidance for value-investing and long-term wealth.
Dr. Charlie Tian is the founder and CEO of GuruFocus.com, a leading global investment research platform established in 2004. With a Ph.D. in physics, Dr. Tian transitioned from science to finance, applying a data-driven, disciplined approach to value investing.
Idemitsu Kosan CoIDKOF 76 Shiller PE Ratio is 10.20 as of Sep. 04, 2026, which is 26% below its 10-year median of 13.77. GuruFocus rates IDKOF with a GF Score™ of 76/100 and a GF Value™ of $6.85 (Modestly Overvalued). The stock has 5 warning signs investors should review. Among 437 Oil & Gas companies, Idemitsu Kosan Co ranks better than 73% on this metric.
The historical rank and industry rank for Idemitsu Kosan Co's Shiller PE Ratio or its related term are showing as below:
IDKOF'
s Shiller PE Ratio Range Over the Past 10 Years
Min: 8.65 Med: 13.77 Max: 34.13
Current: 11.52
During the past years, Idemitsu Kosan Co's highest Shiller PE Ratio was 34.13. The lowest was 8.65. And the median was 13.77.
IDKOF's Shiller PE Ratio is ranked better than 73% of 437
companies
in the Oil & Gas industry
Industry Median: 18.22
vs IDKOF: 11.52
E10 is a concept invented by Prof. Robert Shiller, who uses E10 for his Shiller PE Ratio calculation. E10 is the average of the inflation adjusted earnings of a company over the past 10 years.
Idemitsu Kosan Co's adjusted earnings per share data for the three months ended in Mar. 2026 was $0.614. Add all the adjusted EPS for the past 10 years together and divide 10 will get our E10, which is $0.75 for the trailing ten years ended in Mar. 2026.
Shiller PE for Stocks: The True Measure of Stock Valuation
Idemitsu Kosan Co (OTCPK:IDKOF) Shiller PE Ratio Explanation
Compared with the regular PE Ratio, which works poorly for cyclical businesses, the Shiller PE Ratio smoothed out the fluctuations of profit margins during business cycles. Therefore it is more accurate in reflecting the valuation of the company.
If a company has consistent business performance, the Shiller PE Ratio should give similar results to regular PE Ratio.
Compared with the PS Ratio, the Shiller PE Ratio makes the comparison between different industries more meaningful.
Be Aware
Shiller PE Ratio assumes that over the long term, businesses and profitability revert to their means. If a company's business model does not work in the future compared with the past, Shiller PE Ratio and PS Ratio will give false valuations.
Idemitsu Kosan Co Shiller PE Ratio Related Terms
Idemitsu Kosan Co Shiller PE Ratio Historical Data
* Premium members only.
The historical data trend for Idemitsu Kosan Co's Shiller PE Ratio can be seen below:
* For Operating Data section: All numbers are indicated by the unit behind each term and all currency related amount are in USD. * For other sections: All numbers are in millions except for per share data, ratio, and percentage. All currency related amount are indicated in the company's associated stock exchange currency.
IDKOF vs MPC, VLO, PSX: Shiller PE Ratio Comparison
For the Oil & Gas Refining & Marketing subindustry, Idemitsu Kosan Co's Shiller PE Ratio, along with its competitors' market caps and Shiller PE Ratio data, can be viewed below:
* Competitive companies are chosen from companies within the same industry, with headquarter located in same country, with closest market capitalization; x-axis shows the market cap, and y-axis shows the term value; the bigger the dot, the larger the market cap. Note that "N/A" values will not show up in the chart.
Idemitsu Kosan Co Shiller PE Ratio vs Oil & Gas Industry
For the Oil & Gas industry and Energy sector, Idemitsu Kosan Co's Shiller PE Ratio distribution charts can be found below:
* The bar in red indicates where Idemitsu Kosan Co's Shiller PE Ratio falls into.
For Shiller PE Ratio, the earnings of the past 10 years are inflation-adjusted and averaged. The result is used for P/E calculation. Since it looks at the average over the last 10 years, the Shiller PE Ratio is also called PE10.
The Shiller PE Ratio was first used by professor Robert Shiller to measure the valuation of the overall market. The same calculation is applied here to individual companies.
* For Operating Data section: All numbers are indicated by the unit behind each term and all currency related amount are in USD. * For other sections: All numbers are in millions except for per share data, ratio, and percentage. All currency related amount are indicated in the company's associated stock exchange currency.
Idemitsu Kosan Co's E10 for the quarter that ended in Mar. 2026 is calculated as:
For example, Idemitsu Kosan Co's adjusted earnings per share data for the three months ended in Mar. 2026 was:
Add all the adjusted EPS together and divide 10 will get our E10.
Please note that we use the CPI data of the country/region where the company is headquartered. If the CPI data for that country/region is not available, then we will use the CPI data of the United States as default.
Idemitsu Kosan Co (IDKOF) has a Shiller PE Ratio of 10.20 as of Sep. 04, 2026. Shiller price-earnings ratio is the ratio of share price to a company's inflation-adjusted earnings over a 10-year period. View historical data on Idemitsu Kosan Co and its competitors. This is 26% below median its historical median of 13.77. Over the past decade, Idemitsu Kosan Co's Shiller PE Ratio has ranged from 8.65 to 34.13. According to the industry distribution chart, Idemitsu Kosan Co ranks #118 out of 437 companies in the Oil & Gas industry, placing it in the top 27%.
Is Idemitsu Kosan Co's Shiller PE Ratio too high?
Idemitsu Kosan Co's current Shiller PE Ratio of 10.20 is 26% below median its 10-year median of 13.77. Over the past 10 years, this metric has ranged from a low of 8.65 to a high of 34.13. The Oil & Gas industry median Shiller PE Ratio is 18.22. Idemitsu Kosan Co's value of 10.20 is 44% below this industry median. Based on the distribution chart, Idemitsu Kosan Co ranks #118 out of 437 companies in the Oil & Gas industry, which is above the industry midpoint. Overall, Idemitsu Kosan Co has a GF Score™ of 76/100 and is considered Modestly Overvalued, reflecting its overall financial health beyond just this single metric.
How does Idemitsu Kosan Co's Shiller PE Ratio compare to MPC and VLO?
According to the Oil & Gas industry distribution chart, Idemitsu Kosan Co ranks #118 out of 437 companies for Shiller PE Ratio. This puts Idemitsu Kosan Co in the upper half of its industry. The industry median Shiller PE Ratio is 18.22. Idemitsu Kosan Co's value of 10.20 is 44% below this benchmark. Historically, Idemitsu Kosan Co's own Shiller PE Ratio has ranged from 8.65 to 34.13 over the past decade. While the company's 10-year median is 13.77 vs. the industry median of 18.22, Idemitsu Kosan Co has consistently been below the industry average. See the competitive comparison table and distribution chart on this page for a detailed peer-by-peer breakdown.
What is a good Shiller PE Ratio for an Oil & Gas company?
The median Shiller PE Ratio among Oil & Gas companies is 18.22, based on 437 companies in the industry. Companies in the top quartile (top 25%) have a Shiller PE Ratio significantly above this median, while those in the bottom quartile fall well below. However, Shiller PE Ratio should not be evaluated in isolation — investors should consider it alongside profitability, growth, and financial strength metrics. Idemitsu Kosan Co's current Shiller PE Ratio of 10.20 is 44% below the industry median. Use the industry distribution chart on this page to see where any company falls relative to its peers.
What does a high Shiller PE Ratio mean?
A high Shiller PE Ratio can signal that a stock is expensive relative to its fundamentals. Shiller price-earnings ratio is the ratio of share price to a company's inflation-adjusted earnings over a 10-year period. View historical data on Idemitsu Kosan Co and its competitors. For the Oil & Gas industry, the median Shiller PE Ratio is 18.22 — values significantly above this may indicate overvaluation, while values below may suggest a bargain or underlying issues. Idemitsu Kosan Co's current Shiller PE Ratio is 10.20, which is 26% below median its own 10-year median of 13.77. However, context matters — high-growth companies often justify higher valuations. Always evaluate alongside other metrics like GF Score™ and GF Value™.
Is Idemitsu Kosan Co stock overvalued right now?
Based on GuruFocus' analysis, Idemitsu Kosan Co (IDKOF) is currently considered Modestly Overvalued. The stock's GF Value™ is $6.85, compared to a current price of $7.65 — trading 11.7% above its estimated fair value. The current Shiller PE Ratio is 10.20, which is 26% below median its 10-year median of 13.77 and 44% below the Oil & Gas industry median of 18.22. Idemitsu Kosan Co's overall GF Score™ is 76/100 with 5 warning signs to review. Investors should evaluate multiple metrics — including profitability, growth, and financial strength — before making a decision.
How is Shiller PE Ratio calculated?
Shiller PE Ratio is calculated from a company's financial statements. For Idemitsu Kosan Co (IDKOF), the current Shiller PE Ratio is 10.20 as of Sep. 04, 2026. GuruFocus calculates this using data sourced from SEC filings and annual reports. See the calculation section and 30-year financial data on this page for the full breakdown.
Is Idemitsu Kosan Co (IDKOF) Overvalued in 2026?
Based on GuruFocus' analysis, Idemitsu Kosan Co stock appears to be overvalued.
The current stock price of $7.65 is trading 11.7% above its estimated GF Value™ of $6.85.
GuruFocus considers Idemitsu Kosan Co to be Modestly Overvalued.
Key valuation signals for IDKOF:
Shiller PE Ratio: 10.20 (26% below median its 10-year median of 13.77)
GF Value™: $6.85 vs. price of $7.65 (11.7% above fair value)
Industry Position: 44% below the Oil & Gas median (#118 of 437)
No single metric tells the full story. See the IDKOF stock analysis page for a complete view including 30-year financials, guru trades, and insider activity.
Idemitsu Kosan Co Ltd engages in a variety of activities globally that include petroleum products, oil exploration and production, coal, and other businesses. The company operates through five segments. The Basic Chemicals segment makes and sells olefins and aroma products. Electricity/Renewable Energy covers thermal, solar, and wind power generation, electricity sales, and solar business. Fuel Oil handles production, trading, and import/export of refined petroleum. The Highly Functional Materials segment includes lubricants, chemicals, electronic materials, paving materials, and agri-bio. The Resource segment explores, develops, and sells crude oil, natural gas, and coal. Others cover insurance and intra-group services. It generates the majority of its revenue from the Fuel oil segment.
76GF Score
Get the complete analysis for IDKOF
Shiller PE Ratio is just one metric. See GF Value™, 30-year financials, guru trades, warning signs, and more.
Quick Browse
Personalize
Premium Gurus 
Create New Portfolio
IDKOF has been successfully added to your 
