Calculate and analyze economic growth rates using the chain-weighted method.
Enter the Gross Domestic Product for the most recent year.
Enter the Gross Domestic Product for the preceding year.
Enter the forecasted Gross Domestic Product for the upcoming year.
Enter the price index for the base period (e.g., 100 for the base year).
Enter the average price index for the current year.
Enter the forecasted average price index for the next year.
Your Chain Weighted Growth Analysis
N/A
Real GDP Current Year: N/A
Real GDP Previous Year: N/A
Real GDP Next Year: N/A
Formula Used (Chain Weighted Growth): 1. Calculate Real GDP for each period: Real GDP = (Nominal GDP / Price Index) * Base Year Price Index
2. Calculate Growth Rate: Growth Rate = ((Real GDP Current Year – Real GDP Previous Year) / Real GDP Previous Year) * 100
3. Apply for the next period using forecasts.
Real GDP Growth Projection
Projection of Real GDP over three years using chain weighting.
Key Economic Indicators
Indicator
Value
Unit
Nominal GDP (Previous Year)
N/A
Local Currency
Nominal GDP (Current Year)
N/A
Local Currency
Nominal GDP (Next Year – Forecast)
N/A
Local Currency
Price Index (Previous Year)
N/A
Index Points
Price Index (Current Year)
N/A
Index Points
Price Index (Next Year – Forecast)
N/A
Index Points
Real GDP (Previous Year)
N/A
Local Currency (Base Year Prices)
Real GDP (Current Year)
N/A
Local Currency (Base Year Prices)
Real GDP (Next Year – Forecast)
N/A
Local Currency (Base Year Prices)
Growth Rate (Prev to Curr Year)
N/A
%
Growth Rate (Curr to Next Year – Forecast)
N/A
%
What is Chain Weighted Growth?
Chain weighted growth is an advanced method used in economics to measure the growth of economic output over time, most commonly applied to Gross Domestic Product (GDP). Unlike simple fixed-base year calculations, chain weighting adjusts the base year for calculating real (inflation-adjusted) values on a period-by-period basis. This means that as the economy evolves, the reference prices used to measure real output are updated more frequently, typically annually. This methodology helps to reduce the "substitution bias" that can occur with fixed-base year calculations, where consumers and producers tend to substitute away from goods whose prices have risen significantly. By continuously updating prices, chain-weighted measures provide a more accurate picture of real economic changes, reflecting shifts in consumption patterns and technological advancements more effectively.
Who should use it? Economists, financial analysts, central bankers, policymakers, and students of economics who need to understand and analyze macroeconomic trends with high precision. It's particularly crucial when comparing economic performance over extended periods or across different countries where relative prices might change dramatically. Businesses that rely on accurate economic forecasts for strategic planning, investment decisions, and market analysis also benefit greatly from understanding chain-weighted GDP.
Common misconceptions about chain weighted growth include assuming it is the same as nominal growth (it is not; it adjusts for inflation) or that it perfectly eliminates all sources of bias (while it minimizes substitution bias, other measurement challenges can still exist). Another misconception is that it uses a single, unchanging base year; in reality, the "chain" aspect implies that the reference prices are updated periodically, creating a link between adjacent periods rather than relying on a distant base.
Chain Weighted Growth Formula and Mathematical Explanation
The core idea behind chain weighted growth is to calculate real GDP (GDP adjusted for inflation) by re-weighting the components of GDP using prices from an adjacent period, effectively creating a "chain" of growth rates. Instead of using prices from a single base year for all periods, chain weighting uses prices from the previous period to calculate the real output of the current period.
Here's a step-by-step breakdown:
Calculate Real GDP for Adjacent Periods: For any given period 't', Real GDP is calculated by taking the nominal GDP of period 't' and adjusting it using prices from period 't-1' (the previous period). The formula is typically expressed as:
This formula essentially deflates the current nominal GDP using the current price index and then re-inflates it using the price index from the previous period. This ensures that the quantities of goods and services produced in period 't' are valued at the relative prices of period 't-1'.
Calculate the Period-to-Period Growth Rate: Once you have the real GDP for two consecutive periods (say, t-1 and t), you can calculate the growth rate between them:
Growth Ratet = [ (Real GDPt – Real GDPt-1) / Real GDPt-1 ] * 100
This gives you the percentage change in real output from period t-1 to period t, using the chain-weighted method.
Chain Linking: To get a cumulative growth figure over several periods, these period-to-period growth rates are "chained" together. For example, if you want to find the total growth from period 0 to period 3, you would calculate:
Real GDP (Next Year) = (58,000 / 115) * 100 ≈ 50,435 million
Growth Rate (Curr to Next Year – Forecast) = [(50,435 – 50,926) / 50,926] * 100 ≈ -0.96%
Interpretation:
The economy grew by approximately 1.85% in real terms from the previous year to the current year, despite a significant rise in inflation (8%). However, the forecast for the next year suggests a slight contraction (-0.96%) in real terms, even with continued nominal GDP growth, indicating that inflation is expected to outpace the growth in production. This signals potential economic challenges ahead.
Example 2: Comparing Technological Advancement Impact
Consider a technology-driven economy where new products rapidly change the price structure.
Inputs:
Nominal GDP (Previous Year): 1,200,000 million
Nominal GDP (Current Year): 1,350,000 million
Average Price Index (Previous Year): 110
Average Price Index (Current Year): 125
Nominal GDP (Next Year – Forecast): 1,450,000 million
Average Price Index (Next Year – Forecast): 135
Calculations:
Real GDP (Previous Year) = (1,200,000 / 110) * 110 = 1,200,000 million
Real GDP (Current Year) = (1,350,000 / 125) * 110 ≈ 1,188,000 million
Real GDP (Next Year) = (1,450,000 / 135) * 110 ≈ 1,185,185 million
Growth Rate (Curr to Next Year – Forecast) = [(1,185,185 – 1,188,000) / 1,188,000] * 100 ≈ -0.24%
Interpretation:
Even though nominal GDP grew robustly (12.5% from previous to current year), the chain-weighted real GDP shows a contraction of 1.00%. This is because the price index increased significantly (from 110 to 125), indicating substantial inflation. The rapid adoption of new technologies might have caused prices of older goods to rise disproportionately, or the overall price level increased faster than real output. The forecast shows a slight improvement but still negative growth, suggesting that the high price inflation is expected to continue impacting real output measures. This scenario highlights how chain weighting better captures shifts in relative prices compared to fixed-base measures.
How to Use This Chain Weighted Calculator
Input Nominal GDP Values: Enter the Gross Domestic Product figures for the previous year, the current year, and your forecast for the next year. Ensure these are in the same local currency units.
Input Price Index Values: Provide the average price index for the same three periods: previous year, current year, and next year's forecast. The price index for the base year itself is typically set at 100.
Calculate: Click the "Calculate Growth" button. The calculator will automatically compute the real GDP for each period and the resulting chain-weighted growth rates.
Review Results:
Main Result: The primary highlighted number shows the projected growth rate for the current year to the next year.
Intermediate Values: You'll see the calculated Real GDP for each of the three periods. These are crucial for understanding the underlying inflation-adjusted output.
Table: The detailed table breaks down all input and calculated values, offering a comprehensive overview.
Chart: The dynamic chart visually represents the projected Real GDP trend over the three periods.
Decision Making: Use the calculated growth rates and real GDP figures to assess economic trends. A positive growth rate indicates economic expansion in real terms, while a negative rate suggests contraction. Compare the current year's growth to the forecast to gauge future economic prospects.
Reset and Copy: Use the "Reset" button to clear the fields and start over with default values. The "Copy Results" button allows you to easily transfer the main result, intermediate values, and key assumptions to another document or application.
Key Factors That Affect Chain Weighted Results
Several economic factors significantly influence the calculation and interpretation of chain-weighted growth rates:
Inflation Dynamics: This is the most direct factor. The price indices determine how much nominal GDP is deflated to achieve real GDP. High and volatile inflation requires careful use of chain weighting to avoid misleading real growth figures. Shifts in relative prices during inflationary periods are precisely what chain weighting aims to address.
Changes in Consumption Patterns: As relative prices change, consumers substitute goods. Chain weighting accounts for this by updating the "basket" of goods and services used for price measurement annually. If consumers quickly shift towards cheaper alternatives, chain weighting will reflect this change more accurately than fixed-base methods.
Technological Advancements & New Products: New technologies often lead to improved quality or lower prices for goods (e.g., smartphones). Chain weighting can capture the impact of these changes on real output more effectively by incorporating newer goods and services and their evolving prices into the calculation.
Economic Shocks (Supply and Demand): Unexpected events like natural disasters, pandemics, or geopolitical shifts can drastically alter both nominal GDP and price levels. Chain weighting provides a more responsive measure of real output changes during such turbulent periods by adapting to the new price structure.
Productivity Growth: If an economy becomes more productive, it can produce more output with the same or fewer inputs. Chain weighting measures the real increase in output, reflecting improvements in productivity more accurately, especially when coupled with changes in the relative prices of goods and services produced.
Government Policies (Fiscal & Monetary): Policies that influence inflation, aggregate demand, or supply chains will indirectly affect nominal GDP and price indices. For instance, expansionary fiscal policy might boost nominal GDP but could also fuel inflation, impacting the calculated real growth rate. Monetary policy directly influences inflation expectations and interest rates, which feed into price levels.
International Trade and Exchange Rates: For economies heavily involved in international trade, fluctuations in exchange rates can affect the nominal value of imports and exports, and potentially influence domestic prices. Chain weighting considers these effects as they manifest in the national accounts and price indices.
Frequently Asked Questions (FAQ)
Q1: What is the difference between nominal GDP and real GDP?
Nominal GDP is the value of all final goods and services produced in an economy, measured at current market prices. Real GDP adjusts for inflation, measuring output using prices from a base year or, in the case of chain weighting, prices from an adjacent period. Real GDP provides a clearer picture of the actual volume of goods and services produced.
Q2: Why is chain weighting considered superior to fixed-base weighting?
Chain weighting is generally preferred because it minimizes substitution bias. Fixed-base methods can overstate inflation and understate real growth if the prices of goods in the base year rise much faster than others, causing consumers to switch to relatively cheaper goods. Chain weighting updates the relative prices used in calculations annually, reflecting these substitution effects more accurately.
Q3: Can chain weighting completely eliminate bias?
No, while chain weighting significantly reduces substitution bias, it doesn't eliminate all potential measurement issues. Other biases, such as the introduction of new goods not immediately captured in price indices or quality changes, can still exist. Also, the choice of data sources and methodologies for price indices can introduce their own limitations.
Q4: How often are base prices updated in chain weighting?
Official statistics agencies, like the Bureau of Economic Analysis (BEA) in the U.S., typically update the base prices for chain-weighted GDP calculations annually. This means that each year's real GDP is calculated using the prices from the previous year.
Q5: What does a negative chain-weighted growth rate imply?
A negative chain-weighted growth rate indicates that the economy's real output (inflation-adjusted volume of goods and services) has decreased compared to the previous period. This typically signifies an economic contraction or recession.
Q6: How do I interpret the price index values in the calculator?
The price index measures the relative level of prices. A value of 100 often represents the average price level in a base year. An index of 108 means prices are, on average, 8% higher than in the base year. When calculating real GDP, the price index is used to remove the effect of price changes.
Q7: Can this calculator be used for inflation calculations?
While this calculator focuses on real GDP growth, the price index inputs are directly related to inflation. The change in the price index itself over time indicates the rate of inflation. The calculator uses these inflation measures to derive real growth.
Q8: What is the significance of the 'Base Year Price Index' input?
The 'Base Year Price Index' is used as the reference point for the price index calculation. While the core chain-weighted formula uses adjacent periods' prices, this input helps anchor the price index values and is essential if one were to compare absolute real GDP levels against a specific historical base year, although the primary calculation focuses on growth rates between adjacent periods.
var chartInstance = null; // Global variable to hold chart instance
function validateInput(value, id, errorMessageId, minValue = null, maxValue = null) {
var errorElement = document.getElementById(errorMessageId);
errorElement.style.display = 'none'; // Hide error initially
if (value === null || value === ") {
errorElement.innerText = 'This field cannot be empty.';
errorElement.style.display = 'block';
return false;
}
var numValue = parseFloat(value);
if (isNaN(numValue)) {
errorElement.innerText = 'Please enter a valid number.';
errorElement.style.display = 'block';
return false;
}
if (minValue !== null && numValue maxValue) {
errorElement.innerText = 'Value is out of the acceptable range.';
errorElement.style.display = 'block';
return false;
}
return true;
}
function calculateChainWeightedGrowth() {
var gdpCurrentYear = document.getElementById('gdpCurrentYear').value;
var gdpPreviousYear = document.getElementById('gdpPreviousYear').value;
var gdpNextYear = document.getElementById('gdpNextYear').value;
var baseYearPriceIndex = document.getElementById('baseYearPriceIndex').value; // Not directly used in growth calc, but good for context
var currentYearPriceIndex = document.getElementById('currentYearPriceIndex').value;
var nextYearPriceIndex = document.getElementById('nextYearPriceIndex').value;
// Input validation
var isValid = true;
isValid &= validateInput(gdpCurrentYear, 'gdpCurrentYear', 'gdpCurrentYearError', 0);
isValid &= validateInput(gdpPreviousYear, 'gdpPreviousYear', 'gdpPreviousYearError', 0);
isValid &= validateInput(gdpNextYear, 'gdpNextYear', 'gdpNextYearError', 0);
isValid &= validateInput(baseYearPriceIndex, 'baseYearPriceIndex', 'baseYearPriceIndexError', 0);
isValid &= validateInput(currentYearPriceIndex, 'currentYearPriceIndex', 'currentYearPriceIndexError', 0);
isValid &= validateInput(nextYearPriceIndex, 'nextYearPriceIndex', 'nextYearPriceIndexError', 0);
if (!isValid) {
document.getElementById('mainResult').innerText = 'Invalid Input';
updateTable('N/A');
updateChart([], []);
return;
}
var numGdpCurrent = parseFloat(gdpCurrentYear);
var numGdpPrevious = parseFloat(gdpPreviousYear);
var numGdpNext = parseFloat(gdpNextYear);
var numCurrentPriceIndex = parseFloat(currentYearPriceIndex);
var numNextPriceIndex = parseFloat(nextYearPriceIndex);
// Ensure price indices are not zero to avoid division by zero
if (numCurrentPriceIndex === 0 || numNextPriceIndex === 0 || numGdpPrevious === 0) {
document.getElementById('mainResult').innerText = 'Invalid Index/GDP';
updateTable('N/A');
updateChart([], []);
return;
}
// Calculate Real GDP for each period using the formula: Real GDP_t = (Nominal GDP_t / Price Index_t) * Base Year Price Index
// For growth rate, we need Real GDP_t relative to Real GDP_{t-1}. The simplest way is to use the *previous* period's price index as the base for the *current* period's real GDP calculation.
// Real GDP (Previous Year) = (Nominal GDP Previous Year / Price Index Previous Year) * Price Index Previous Year = Nominal GDP Previous Year (for context, though not strictly needed for growth calc if using adjacent prices)
// For chain weighting, it's more about comparing real values derived from adjacent prices.
// Let's use the standard approach for chain-weighted growth:
// Real GDP_t (valued at t-1 prices) = Nominal GDP_t * (Price Index_{t-1} / Price Index_t)
// This is equivalent to (Nominal GDP_t / Price Index_t) * Price Index_{t-1} if the "base" for the price index itself is consistent.
// Let's assume the 'baseYearPriceIndex' is indeed the index value for the *previous* year when calculating current year's real GDP.
// Correction: The standard chain-weighted definition uses prices from the *previous* period to value the *current* period's output.
// Real GDP_Current (using Previous Year's prices) = Nominal GDP_Current * (Price Index_Previous / Price Index_Current)
// Real GDP_Next (using Current Year's prices) = Nominal GDP_Next * (Price Index_Current / Price Index_Next)
var realGdpPreviousYear = numGdpPrevious; // Assuming previous year's nominal GDP is the baseline if we want to compare to it.
// OR, calculate Real GDP Previous Year if we had data for t-2.
// For this calculator, we'll use nominal prev year GDP as the base for the *first* growth calculation, and then calculated real GDPs for subsequent ones.
// Let's recalculate Real GDP values for clarity and correct chain application:
// We need a consistent base for calculating "real" values across all periods. The common practice is to use prices from *previous* period to calculate *current* period's real GDP.
// For Growth Rate (Prev to Curr Year):
// Real GDP_Prev (valued at some base prices, e.g., Prev Year Prices) = Nominal GDP_Prev
// Real GDP_Curr (valued at Prev Year Prices) = Nominal GDP_Curr * (Price Index_Prev / Price Index_Curr)
var realGdpCurrentAdjusted = numGdpCurrent * (parseFloat(document.getElementById('baseYearPriceIndex').value) / numCurrentPriceIndex);
var realGdpPreviousAdjusted = numGdpPrevious * (parseFloat(document.getElementById('baseYearPriceIndex').value) / parseFloat(document.getElementById('baseYearPriceIndex').value)); // This assumes baseYearPriceIndex IS the price index for the previous year for the first calculation. Let's simplify.
// Let's assume for simplicity, we use the *given* previous year price index to value the current year's nominal GDP.
// Real GDP_Current = Nominal GDP_Current * (Price Index_Previous / Price Index_Current)
var realGdpCurrent = numGdpCurrent * (parseFloat(document.getElementById('baseYearPriceIndex').value) / numCurrentPriceIndex);
// Real GDP_Previous = Nominal GDP_Previous * (Price Index_Prev_Prev / Price Index_Previous). This gets complicated quickly.
// A common simplification is:
// Real GDP_Current Year = Nominal GDP Current Year * (Price Index Base Year / Price Index Current Year)
// Real GDP_Previous Year = Nominal GDP Previous Year * (Price Index Base Year / Price Index Previous Year)
// This is standard GDP deflator method. CHAIN WEIGHTING uses PRICES FROM PREVIOUS PERIOD.
// Let's use the formula: Real GDP_t = Nominal GDP_t * (Price Index_{t-1} / Price Index_t)
// For our inputs:
// Period 1: Previous Year
// Period 2: Current Year
// Period 3: Next Year
// We need price index for Previous Year (let's use input 'baseYearPriceIndex' for this purpose)
// And price index for Current Year (input 'currentYearPriceIndex')
// And price index for Next Year (input 'nextYearPriceIndex')
// Nominal GDP values: gdpPreviousYear, gdpCurrentYear, gdpNextYear
// Real GDP for Previous Year (valued at Previous Year's prices): This is just the nominal GDP Previous Year if we consider its own prices as base.
var realGdpPrev = numGdpPrevious; // Use nominal previous year GDP as reference point.
// Real GDP for Current Year (valued at Previous Year's prices):
var realGdpCurr = numGdpCurrent * (parseFloat(document.getElementById('baseYearPriceIndex').value) / numCurrentPriceIndex);
// Real GDP for Next Year (valued at Current Year's prices):
var realGdpNext = numGdpNext * (numCurrentPriceIndex / numNextPriceIndex);
// Growth Rate (Prev to Curr Year):
var growthRatePrevCurr = 0;
if (realGdpPrev !== 0) {
growthRatePrevCurr = ((realGdpCurr – realGdpPrev) / realGdpPrev) * 100;
}
// Growth Rate (Curr to Next Year – Forecast):
var growthRateCurrNext = 0;
if (realGdpCurr !== 0) {
growthRateCurrNext = ((realGdpNext – realGdpCurr) / realGdpCurr) * 100;
}
document.getElementById('mainResult').innerText = growthRateCurrNext.toFixed(2) + '%';
document.getElementById('realGdpCurrent').getElementsByTagName('span')[0].innerText = realGdpCurr.toFixed(2);
document.getElementById('realGdpPrevious').getElementsByTagName('span')[0].innerText = realGdpPrev.toFixed(2);
document.getElementById('realGdpNext').getElementsByTagName('span')[0].innerText = realGdpNext.toFixed(2);
updateTable(
numGdpPrevious.toFixed(2),
numGdpCurrent.toFixed(2),
numGdpNext.toFixed(2),
parseFloat(document.getElementById('baseYearPriceIndex').value).toFixed(2),
numCurrentPriceIndex.toFixed(2),
numNextPriceIndex.toFixed(2),
realGdpPrev.toFixed(2),
realGdpCurr.toFixed(2),
realGdpNext.toFixed(2),
growthRatePrevCurr.toFixed(2),
growthRateCurrNext.toFixed(2)
);
updateChart([realGdpPrev, realGdpCurr, realGdpNext], [growthRatePrevCurr, growthRateCurrNext]);
}
function updateTable(nomPrev, nomCurr, nomNext, pricePrev, priceCurr, priceNext, realPrev, realCurr, realNext, growthPrevCurr, growthCurrNext) {
document.getElementById('tableNominalPrev').innerText = nomPrev;
document.getElementById('tableNominalCurr').innerText = nomCurr;
document.getElementById('tableNominalNext').innerText = nomNext;
document.getElementById('tablePricePrev').innerText = pricePrev;
document.getElementById('tablePriceCurr').innerText = priceCurr;
document.getElementById('tablePriceNext').innerText = priceNext;
document.getElementById('tableRealPrev').innerText = realPrev;
document.getElementById('tableRealCurr').innerText = realCurr;
document.getElementById('tableRealNext').innerText = realNext;
document.getElementById('tableGrowthPrevCurr').innerText = growthPrevCurr;
document.getElementById('tableGrowthCurrNext').innerText = growthCurrNext;
}
function updateChart(realGdpValues, growthRates) {
var ctx = document.getElementById('gdpChart').getContext('2d');
// Destroy previous chart instance if it exists
if (chartInstance) {
chartInstance.destroy();
}
var labels = ['Previous Year', 'Current Year', 'Next Year (Forecast)'];
var dataRealGdp = realGdpValues; // [realGdpPrev, realGdpCurr, realGdpNext]
var dataGrowthRates = growthRates; // [growthRatePrevCurr, growthRateCurrNext] – need to adjust for chart display
// For growth rate series, we need values for each period.
// Period 1 Growth: Use 0 or NaN as there's no prior period in our calculation scope.
// Period 2 Growth: growthRatePrevCurr
// Period 3 Growth: growthRateCurrNext
var displayGrowthRates = [NaN, dataGrowthRates[0] || 0, dataGrowthRates[1] || 0];
chartInstance = new Chart(ctx, {
type: 'bar', // Use bar chart for distinct periods
data: {
labels: labels,
datasets: [{
label: 'Real GDP (in Previous Year Prices)',
data: dataRealGdp,
backgroundColor: 'rgba(0, 74, 153, 0.6)', // Primary color
borderColor: 'rgba(0, 74, 153, 1)',
borderWidth: 1,
yAxisID: 'y-axis-gdp'
},
{
label: 'Year-over-Year Growth (%)',
data: displayGrowthRates,
backgroundColor: 'rgba(40, 167, 69, 0.6)', // Success color
borderColor: 'rgba(40, 167, 69, 1)',
borderWidth: 1,
type: 'line', // Overlay line chart for growth
fill: false,
yAxisID: 'y-axis-growth'
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
x: {
grid: {
display: false
}
},
'y-axis-gdp': {
type: 'linear',
position: 'left',
title: {
display: true,
text: 'Real GDP (Local Currency)'
},
ticks: {
callback: function(value) {
if (value % 10000 === 0) return value / 1000 + 'k'; // Format large numbers
return null;
}
}
},
'y-axis-growth': {
type: 'linear',
position: 'right',
title: {
display: true,
text: 'Growth Rate (%)'
},
grid: {
drawOnChartArea: false, // Only display grid lines for the primary y-axis
},
ticks: {
callback: function(value) {
return value + '%';
}
}
}
},
plugins: {
tooltip: {
mode: 'index',
intersect: false,
callbacks: {
label: function(context) {
var label = context.dataset.label || ";
if (label) {
label += ': ';
}
if (context.parsed.y !== null) {
if (context.dataset.label.includes('%')) {
label += context.parsed.y.toFixed(2) + '%';
} else {
label += context.parsed.y.toFixed(2);
}
}
return label;
}
}
},
legend: {
position: 'bottom',
}
}
}
});
}
function resetCalculator() {
document.getElementById('gdpCurrentYear').value = '11000';
document.getElementById('gdpPreviousYear').value = '10000';
document.getElementById('gdpNextYear').value = '11500';
document.getElementById('baseYearPriceIndex').value = '100';
document.getElementById('currentYearPriceIndex').value = '105';
document.getElementById('nextYearPriceIndex').value = '110';
document.getElementById('mainResult').innerText = 'N/A';
document.getElementById('realGdpCurrent').getElementsByTagName('span')[0].innerText = 'N/A';
document.getElementById('realGdpPrevious').getElementsByTagName('span')[0].innerText = 'N/A';
document.getElementById('realGdpNext').getElementsByTagName('span')[0].innerText = 'N/A';
updateTable('N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A');
updateChart([], []);
// Clear error messages
var errorElements = document.querySelectorAll('.error-message');
for (var i = 0; i < errorElements.length; i++) {
errorElements[i].style.display = 'none';
errorElements[i].innerText = '';
}
}
function copyResults() {
var mainResult = document.getElementById('mainResult').innerText;
var realGdpPrev = document.getElementById('realGdpPrevious').getElementsByTagName('span')[0].innerText;
var realGdpCurr = document.getElementById('realGdpCurrent').getElementsByTagName('span')[0].innerText;
var realGdpNext = document.getElementById('realGdpNext').getElementsByTagName('span')[0].innerText;
var assumptions = "Assumptions:\n";
assumptions += "GDP Previous Year: " + document.getElementById('gdpPreviousYear').value + "\n";
assumptions += "GDP Current Year: " + document.getElementById('gdpCurrentYear').value + "\n";
assumptions += "GDP Next Year (Forecast): " + document.getElementById('gdpNextYear').value + "\n";
assumptions += "Price Index Previous Year: " + document.getElementById('baseYearPriceIndex').value + "\n";
assumptions += "Price Index Current Year: " + document.getElementById('currentYearPriceIndex').value + "\n";
assumptions += "Price Index Next Year (Forecast): " + document.getElementById('nextYearPriceIndex').value + "\n";
var resultsText = "Chain Weighted Growth Results:\n";
resultsText += "—————————–\n";
resultsText += "Forecasted Growth Rate (Current to Next Year): " + mainResult + "\n\n";
resultsText += "Intermediate Real GDP:\n";
resultsText += "Real GDP (Previous Year): " + realGdpPrev + "\n";
resultsText += "Real GDP (Current Year): " + realGdpCurr + "\n";
resultsText += "Real GDP (Next Year): " + realGdpNext + "\n\n";
resultsText += assumptions;
// Use a temporary textarea to copy text to clipboard
var textArea = document.createElement("textarea");
textArea.value = resultsText;
textArea.style.position = "fixed";
textArea.style.left = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied to clipboard!' : 'Copying failed!';
// Optional: Show a temporary message to the user
console.log(msg);
// Add a temporary visual feedback element
var feedback = document.createElement('div');
feedback.textContent = msg;
feedback.style.cssText = 'position: fixed; top: 50%; left: 50%; transform: translate(-50%, -50%); background-color: var(–primary-color); color: white; padding: 15px; border-radius: 5px; z-index: 1000; font-size: 1.1em; box-shadow: 0 0 10px rgba(0,0,0,0.3);';
document.body.appendChild(feedback);
setTimeout(function() {
feedback.remove();
}, 3000);
} catch (err) {
console.error('Fallback: Oops, unable to copy', err);
// Optional: Inform user if copy command fails
alert('Could not copy text. Please copy manually.');
}
document.body.removeChild(textArea);
}
// Initial calculation on page load
document.addEventListener('DOMContentLoaded', function() {
// Include Chart.js library dynamically
var script = document.createElement('script');
script.src = 'https://cdn.jsdelivr.net/npm/chart.js@4.4.1/dist/chart.umd.min.js'; // Use Chart.js v4
script.onload = function() {
console.log("Chart.js loaded successfully.");
calculateChainWeightedGrowth(); // Perform calculation after Chart.js is loaded
};
script.onerror = function() {
console.error("Failed to load Chart.js library.");
};
document.head.appendChild(script);
// Add event listeners for real-time updates (optional, if needed beyond button click)
var inputs = document.querySelectorAll('.loan-calc-container input[type="number"]');
for (var i = 0; i < inputs.length; i++) {
inputs[i].addEventListener('input', calculateChainWeightedGrowth);
}
});