Consulting guesstimate exercise refers to making quick, educated estimates in business scenarios, often used in case interviews.

Two main approaches:

  1. Top-down: Start with a large, known number and break it down. Example: Estimating coffee shop customers by starting with city population.

  2. Bottom-up: Build up from smaller, known quantities. Example: Estimating coffee shop customers by calculating customers per hour, then extrapolating to a day.

Both methods help in making reasonable estimates when exact data isn't available.

Estimate the number of smartphones sold in India in a year

Top-Down Approach

  1. Start with the Total Population:

    • India's population: ~1.4 billion.

  2. Determine the Percentage of Smartphone Users:

    • Assume around 50% of the population uses smartphones (based on market penetration data).

    • Smartphone users = 1.4 billion * 50% = 700 million.

  3. Estimate the Average Replacement Cycle:

    • Assume the average smartphone replacement cycle is every 2 years.

    • Therefore, each year, about half of the smartphone users will replace their phones.

    • Number of smartphones replaced each year = 700 million / 2 = 350 million.

  4. Consider New Users:

    • Assume 5% of the population becomes new smartphone users each year.

    • New smartphone users per year = 1.4 billion * 5% = 70 million.

  5. Sum the Replacement and New Sales:

    • Total smartphones sold in a year = Replacements + New users.

    • Total = 350 million + 70 million = 420 million.

Top-Down Approach

  1. Start with the Total Population:

    • India's population: ~1.4 billion.

  2. Determine the Percentage of Smartphone Users:

    • Assume around 50% of the population uses smartphones (based on market penetration data).

    • Smartphone users = 1.4 billion * 50% = 700 million.

  3. Estimate the Average Replacement Cycle:

    • Assume the average smartphone replacement cycle is every 2 years.

    • Therefore, each year, about half of the smartphone users will replace their phones.

    • Number of smartphones replaced each year = 700 million / 2 = 350 million.

  4. Consider New Users:

    • Assume 5% of the population becomes new smartphone users each year.

    • New smartphone users per year = 1.4 billion * 5% = 70 million.

  5. Sum the Replacement and New Sales:

    • Total smartphones sold in a year = Replacements + New users.

    • Total = 350 million + 70 million = 420 million.

Bottom-Up Approach

  1. Identify Key Segments of the Population:

    • Urban population: ~35% of 1.4 billion = 490 million.

    • Rural population: ~65% of 1.4 billion = 910 million.

  2. Estimate Smartphone Penetration in Each Segment:

    • Urban smartphone penetration: 70%.

    • Rural smartphone penetration: 30%.

  3. Calculate the Number of Smartphone Users in Each Segment:

    • Urban smartphone users = 490 million * 70% = 343 million.

    • Rural smartphone users = 910 million * 30% = 273 million.

    • Total smartphone users = 343 million + 273 million = 616 million.

  4. Estimate the Replacement Cycle and New Users:

    • Assume urban users replace their phones every 1.5 years.

    • Assume rural users replace their phones every 3 years.

    • Urban replacements per year = 343 million / 1.5 = 229 million.

    • Rural replacements per year = 273 million / 3 = 91 million.

  5. Estimate New Users in Each Segment:

    • Assume 7% of the urban population becomes new smartphone users each year.

    • Assume 3% of the rural population becomes new smartphone users each year.

    • New urban users = 490 million * 7% = 34.3 million.

    • New rural users = 910 million * 3% = 27.3 million.

    • Total new users = 34.3 million + 27.3 million = 61.6 million.

  6. Sum the Replacement and New Sales:

    • Total smartphones sold in a year = Urban replacements + Rural replacements + New users.

    • Total = 229 million + 91 million + 61.6 million = 381.6 million.

Bottom-Up Approach

  1. Identify Key Segments of the Population:

    • Urban population: ~35% of 1.4 billion = 490 million.

    • Rural population: ~65% of 1.4 billion = 910 million.

  2. Estimate Smartphone Penetration in Each Segment:

    • Urban smartphone penetration: 70%.

    • Rural smartphone penetration: 30%.

  3. Calculate the Number of Smartphone Users in Each Segment:

    • Urban smartphone users = 490 million * 70% = 343 million.

    • Rural smartphone users = 910 million * 30% = 273 million.

    • Total smartphone users = 343 million + 273 million = 616 million.

  4. Estimate the Replacement Cycle and New Users:

    • Assume urban users replace their phones every 1.5 years.

    • Assume rural users replace their phones every 3 years.

    • Urban replacements per year = 343 million / 1.5 = 229 million.

    • Rural replacements per year = 273 million / 3 = 91 million.

  5. Estimate New Users in Each Segment:

    • Assume 7% of the urban population becomes new smartphone users each year.

    • Assume 3% of the rural population becomes new smartphone users each year.

    • New urban users = 490 million * 7% = 34.3 million.

    • New rural users = 910 million * 3% = 27.3 million.

    • Total new users = 34.3 million + 27.3 million = 61.6 million.

  6. Sum the Replacement and New Sales:

    • Total smartphones sold in a year = Urban replacements + Rural replacements + New users.

    • Total = 229 million + 91 million + 61.6 million = 381.6 million.

Summary

Top-Down Approach: Estimated 420 million smartphones sold in a year.Bottom-Up Approach: Estimated 381.6 million smartphones sold in a year.Both approaches provide a structured way to tackle the guesstimate problem, with slight variations in the final numbers due to different assumptions and segmentation.

Summary

Top-Down Approach: Estimated 420 million smartphones sold in a year.Bottom-Up Approach: Estimated 381.6 million smartphones sold in a year.Both approaches provide a structured way to tackle the guesstimate problem, with slight variations in the final numbers due to different assumptions and segmentation.

Guesstimate Problem-Solving Framework

1. Initial Planning

  • Identify key variables (30 sec)

  • Choose Top Down or Bottom Up

1. Initial Planning

  • Identify key variables (30 sec)

  • Choose Top Down or Bottom Up

2. Variable Identification

  • List all relevant variables

  • Segment problem (supply/demand)

2. Variable Identification

  • List all relevant variables

  • Segment problem (supply/demand)

3. Assumption Justification

  • Back assumptions with reason

  • Limit assumptions, use facts

3. Assumption Justification

  • Back assumptions with reason

  • Limit assumptions, use facts

4. Structured Approach

  • Maintain organized thinking

  • Validate before computing

4. Structured Approach

  • Maintain organized thinking

  • Validate before computing

5. Communication

  • Convey logic clearly

  • Segregate facts and assumptions

5. Communication

  • Convey logic clearly

  • Segregate facts and assumptions

6. Adaptability

  • Make quick decisions

  • Use exclusive information

6. Adaptability

  • Make quick decisions

  • Use exclusive information

Consulting guesstimate exercise refers to making quick, educated estimates in business scenarios, often used in case interviews.

Two main approaches:

  1. Top-down: Start with a large, known number and break it down. Example: Estimating coffee shop customers by starting with city population.

  2. Bottom-up: Build up from smaller, known quantities. Example: Estimating coffee shop customers by calculating customers per hour, then extrapolating to a day.

Both methods help in making reasonable estimates when exact data isn't available.

Estimate the number of smartphones sold in India in a year

Top-Down Approach

  1. Start with the Total Population:

    • India's population: ~1.4 billion.

  2. Determine the Percentage of Smartphone Users:

    • Assume around 50% of the population uses smartphones (based on market penetration data).

    • Smartphone users = 1.4 billion * 50% = 700 million.

  3. Estimate the Average Replacement Cycle:

    • Assume the average smartphone replacement cycle is every 2 years.

    • Therefore, each year, about half of the smartphone users will replace their phones.

    • Number of smartphones replaced each year = 700 million / 2 = 350 million.

  4. Consider New Users:

    • Assume 5% of the population becomes new smartphone users each year.

    • New smartphone users per year = 1.4 billion * 5% = 70 million.

  5. Sum the Replacement and New Sales:

    • Total smartphones sold in a year = Replacements + New users.

    • Total = 350 million + 70 million = 420 million.

Bottom-Up Approach

  1. Identify Key Segments of the Population:

    • Urban population: ~35% of 1.4 billion = 490 million.

    • Rural population: ~65% of 1.4 billion = 910 million.

  2. Estimate Smartphone Penetration in Each Segment:

    • Urban smartphone penetration: 70%.

    • Rural smartphone penetration: 30%.

  3. Calculate the Number of Smartphone Users in Each Segment:

    • Urban smartphone users = 490 million * 70% = 343 million.

    • Rural smartphone users = 910 million * 30% = 273 million.

    • Total smartphone users = 343 million + 273 million = 616 million.

  4. Estimate the Replacement Cycle and New Users:

    • Assume urban users replace their phones every 1.5 years.

    • Assume rural users replace their phones every 3 years.

    • Urban replacements per year = 343 million / 1.5 = 229 million.

    • Rural replacements per year = 273 million / 3 = 91 million.

  5. Estimate New Users in Each Segment:

    • Assume 7% of the urban population becomes new smartphone users each year.

    • Assume 3% of the rural population becomes new smartphone users each year.

    • New urban users = 490 million * 7% = 34.3 million.

    • New rural users = 910 million * 3% = 27.3 million.

    • Total new users = 34.3 million + 27.3 million = 61.6 million.

  6. Sum the Replacement and New Sales:

    • Total smartphones sold in a year = Urban replacements + Rural replacements + New users.

    • Total = 229 million + 91 million + 61.6 million = 381.6 million.

Summary

Top-Down Approach: Estimated 420 million smartphones sold in a year.Bottom-Up Approach: Estimated 381.6 million smartphones sold in a year.Both approaches provide a structured way to tackle the guesstimate problem, with slight variations in the final numbers due to different assumptions and segmentation.

Guesstimate Problem-Solving Framework

1. Initial Planning

  • Identify key variables (30 sec)

  • Choose Top Down or Bottom Up

2. Variable Identification

  • List all relevant variables

  • Segment problem (supply/demand)

3. Assumption Justification

  • Back assumptions with reason

  • Limit assumptions, use facts

4. Structured Approach

  • Maintain organized thinking

  • Validate before computing

5. Communication

  • Convey logic clearly

  • Segregate facts and assumptions

6. Adaptability

  • Make quick decisions

  • Use exclusive information