diff --git a/docs/api-reference.md b/docs/api-reference.md
index 1425503..c6f7a16 100644
--- a/docs/api-reference.md
+++ b/docs/api-reference.md
@@ -11,7 +11,7 @@ const client = new NodeTSNClient({
   endpoint: "https://staging.tsn.truflation.com",
   signerInfo: {
     address: wallet.address,
-    signer: wallet,  // Must implement signMessage (e.g. ethers Wallet)
+    signer: wallet, // Must implement signMessage (e.g. ethers Wallet)
   },
   chainId: "tsn-1",
 });
@@ -32,21 +32,29 @@ const type = await stream.getType(); // Returns StreamType
 const records = await stream.getRecord({
   dateFrom: "2024-01-01",
   dateTo: "2024-01-31",
-  frozenAt: 12345  // Optional block height
+  frozenAt: 12345, // Optional block height
 });
 
 // Get stream index
 const index = await stream.getIndex({
-  dateFrom: "2024-01-01", 
+  dateFrom: "2024-01-01",
   dateTo: "2024-01-31",
-  baseDate: "2023-12-31"
+  baseDate: "2023-12-31",
 });
 
 // Get first record
 const firstRecord = await stream.getFirstRecord({
   afterDate: "2024-01-01",
-  frozenAt: 12345
+  frozenAt: 12345,
 }); // Returns StreamRecord | null
+
+// Calculate year-over-year changes
+const changes = await stream.getIndexChange({
+  dateFrom: "2024-01-01",
+  dateTo: "2024-12-31",
+  daysInterval: 365,
+  baseDate: "2024-01-01",
+}); // Returns StreamRecord[]
 ```
 
 ### Primitive Stream Operations
@@ -56,7 +64,7 @@ const primitiveStream = client.loadPrimitiveStream(streamLocator);
 
 // Insert data
 await primitiveStream.insertRecords([
-  { dateValue: "2024-01-01", value: "100.5" }
+  { dateValue: "2024-01-01", value: "100.5" },
 ]);
 ```
 
@@ -70,15 +78,15 @@ await composedStream.setTaxonomy({
   taxonomyItems: [
     {
       childStream: childStreamLocator,
-      weight: "1.5"
-    }
+      weight: "1.5",
+    },
   ],
-  startDate: "2024-01-01" // Optional
+  startDate: "2024-01-01", // Optional
 });
 
 // Get taxonomy
 const taxonomy = await composedStream.describeTaxonomies({
-  latestVersion: true
+  latestVersion: true,
 });
 ```
 
@@ -119,5 +127,4 @@ const allStreams = await client.getAllStreams();
 const ownerStreams = await client.getAllStreams(ownerAddress);
 ```
 
-
 For comprehensive examples of these APIs in use, please check our [integration tests](../tests/integration).
diff --git a/src/contracts-api/stream.ts b/src/contracts-api/stream.ts
index 03c5f1e..a2f19e7 100644
--- a/src/contracts-api/stream.ts
+++ b/src/contracts-api/stream.ts
@@ -36,6 +36,10 @@ export interface StreamRecord {
   value: string;
 }
 
+export interface GetIndexChangeInput extends GetRecordInput {
+  daysInterval: number;
+}
+
 export class Stream {
   protected kwilClient: WebKwil | NodeKwil;
   protected kwilSigner: KwilSigner;
@@ -482,4 +486,33 @@ export class Stream {
         };
       });
   }
+
+  /**
+   * Returns the index change of the stream within the given date range
+   */
+  public async getIndexChange(
+    input: GetIndexChangeInput,
+  ): Promise<StreamRecord[]> {
+    const result = await this.call<{ date_value: string; value: string }[]>(
+      "get_index_change",
+      [
+        ActionInput.fromObject({
+          $date_from: input.dateFrom,
+          $date_to: input.dateTo,
+          $frozen_at: input.frozenAt,
+          $base_date: input.baseDate,
+          $days_interval: input.daysInterval,
+        }),
+      ],
+    );
+
+    return result
+      .mapRight((result) =>
+        result.map((row) => ({
+          dateValue: row.date_value,
+          value: row.value,
+        })),
+      )
+      .throw();
+  }
 }
diff --git a/tests/integration/primitiveStream.test.ts b/tests/integration/primitiveStream.test.ts
index 2a61e76..1800c82 100644
--- a/tests/integration/primitiveStream.test.ts
+++ b/tests/integration/primitiveStream.test.ts
@@ -79,5 +79,69 @@ describe.sequential(
         }
       },
     );
+
+    testWithDefaultWallet(
+      "should calculate index changes correctly",
+      async ({ defaultClient }) => {
+        // Generate a unique stream ID
+        const streamId = await StreamId.generate("test-primitive-stream");
+
+        try {
+          // Deploy and initialize stream
+          await defaultClient.deployStream(streamId, "primitive", true);
+          const primitiveStream = defaultClient.loadPrimitiveStream({
+            streamId,
+            dataProvider: defaultClient.address(),
+          });
+          const initTx = await primitiveStream.initializeStream();
+          await defaultClient.waitForTx(initTx.data!.tx_hash!);
+
+          // Insert historical records (2022)
+          const historicalRecords = [
+            { dateValue: "2022-01-01", value: "100" },
+            { dateValue: "2022-06-01", value: "120" },
+            { dateValue: "2022-12-01", value: "150" },
+          ];
+          const historicalTx =
+            await primitiveStream.insertRecords(historicalRecords);
+          await defaultClient.waitForTx(historicalTx.data!.tx_hash!);
+
+          // Insert current records (2023)
+          const currentRecords = [
+            { dateValue: "2023-01-01", value: "200" },
+            { dateValue: "2023-06-01", value: "180" },
+            { dateValue: "2023-12-01", value: "240" },
+          ];
+          const currentTx = await primitiveStream.insertRecords(currentRecords);
+          await defaultClient.waitForTx(currentTx.data!.tx_hash!);
+
+          // Calculate year-over-year changes
+          const changes = await primitiveStream.getIndexChange({
+            dateFrom: "2023-01-01",
+            dateTo: "2023-12-31",
+            daysInterval: 365,
+            baseDate: "2022-01-01",
+          });
+
+          // Verify the changes
+          expect(changes.length).toBe(3);
+
+          // 2023-01-01 vs 2022-01-01: ((200 - 100) / 100) * 100 = 100%
+          expect(changes[0].dateValue).toBe("2023-01-01");
+          expect(parseFloat(changes[0].value)).toBeCloseTo(100);
+
+          // 2023-06-01 vs 2022-06-01: ((180 - 120) / 120) * 100 = 50%
+          expect(changes[1].dateValue).toBe("2023-06-01");
+          expect(parseFloat(changes[1].value)).toBeCloseTo(50);
+
+          // 2023-12-01 vs 2022-12-01: ((240 - 150) / 150) * 100 = 60%
+          expect(changes[2].dateValue).toBe("2023-12-01");
+          expect(parseFloat(changes[2].value)).toBeCloseTo(60);
+        } finally {
+          // Cleanup
+          await defaultClient.destroyStream(streamId, true);
+        }
+      },
+    );
   },
 );