diff --git a/src/Model/Stats/AllResponse.php b/src/Model/Stats/AllResponse.php
index d6ee408..6d63b1f 100644
--- a/src/Model/Stats/AllResponse.php
+++ b/src/Model/Stats/AllResponse.php
@@ -18,30 +18,14 @@ use Mailgun\Model\ApiResponse;
  */
 final class AllResponse implements ApiResponse
 {
-    /**
-     * @var int
-     */
     private $totalCount;
-
-    /**
-     * @var AllResponseItem[]
-     */
     private $items;
 
-    /**
-     * @param int               $totalCount
-     * @param AllResponseItem[] $items
-     */
-    private function __construct($totalCount, array $items)
+    private function __construct()
     {
-        $this->totalCount = $totalCount;
-        $this->items = $items;
     }
 
-    /**
-     * @return self
-     */
-    public static function create(array $data)
+    public static function create(array $data): self
     {
         $items = [];
         if (isset($data['items'])) {
@@ -50,19 +34,14 @@ final class AllResponse implements ApiResponse
             }
         }
 
-        if (isset($data['total_count'])) {
-            $count = $data['total_count'];
-        } else {
-            $count = count($items);
-        }
+        $model = new self();
+        $model->totalCount = (int) ($data['total_count'] ?? count($items));
+        $model->items = $items;
 
-        return new self($count, $items);
+        return $model;
     }
 
-    /**
-     * @return int
-     */
-    public function getTotalCount()
+    public function getTotalCount(): int
     {
         return $this->totalCount;
     }
@@ -70,7 +49,7 @@ final class AllResponse implements ApiResponse
     /**
      * @return AllResponseItem[]
      */
-    public function getItems()
+    public function getItems(): array
     {
         return $this->items;
     }
diff --git a/src/Model/Stats/AllResponseItem.php b/src/Model/Stats/AllResponseItem.php
index d248dfe..d00da66 100644
--- a/src/Model/Stats/AllResponseItem.php
+++ b/src/Model/Stats/AllResponseItem.php
@@ -16,80 +16,39 @@ namespace Mailgun\Model\Stats;
  */
 final class AllResponseItem
 {
-    /**
-     * @var string
-     */
     private $id;
-
-    /**
-     * @var string
-     */
     private $event;
-
-    /**
-     * @var string
-     */
     private $totalCount;
-
-    /**
-     * @var string[]
-     */
     private $tags;
-
-    /**
-     * @var \DateTime
-     */
     private $createdAt;
 
-    /**
-     * @return self
-     */
-    public static function create(array $data)
+    public static function create(array $data): self
     {
-        return new self(
-            isset($data['id']) ? $data['id'] : null,
-            isset($data['event']) ? $data['event'] : null,
-            isset($data['total_count']) ? $data['total_count'] : null,
-            isset($data['tags']) ? $data['tags'] : null,
-            isset($data['created_at']) ? new \DateTime($data['created_at']) : null
-        );
+        $model = new self();
+        $model->id = $data['id'] ?? null;
+        $model->event = $data['event'] ?? null;
+        $model->totalCount = (int) ($data['total_count'] ?? 0);
+        $model->tags = $data['tags'] ?? [];
+        $model->createdAt = isset($data['created_at']) ? new \DateTimeImmutable($data['created_at']) : null;
+
+        return $model;
     }
 
-    /**
-     * @param string   $id
-     * @param string   $event
-     * @param string   $totalCount
-     * @param string[] $tags
-     */
-    private function __construct($id, $event, $totalCount, array $tags, \DateTime $createdAt)
+    private function __construct()
     {
-        $this->id = $id;
-        $this->event = $event;
-        $this->totalCount = $totalCount;
-        $this->tags = $tags;
-        $this->createdAt = $createdAt;
     }
 
-    /**
-     * @return string
-     */
-    public function getId()
+    public function getId(): ?string
     {
         return $this->id;
     }
 
-    /**
-     * @return string
-     */
-    public function getEvent()
+    public function getEvent(): ?string
     {
         return $this->event;
     }
 
-    /**
-     * @return string
-     */
-    public function getTotalCount()
+    public function getTotalCount(): int
     {
         return $this->totalCount;
     }
@@ -97,15 +56,12 @@ final class AllResponseItem
     /**
      * @return string[]
      */
-    public function getTags()
+    public function getTags(): array
     {
         return $this->tags;
     }
 
-    /**
-     * @return \DateTime
-     */
-    public function getCreatedAt()
+    public function getCreatedAt(): ?\DateTimeImmutable
     {
         return $this->createdAt;
     }
diff --git a/src/Model/Stats/TotalResponse.php b/src/Model/Stats/TotalResponse.php
index f6b1d2e..ed23574 100644
--- a/src/Model/Stats/TotalResponse.php
+++ b/src/Model/Stats/TotalResponse.php
@@ -18,42 +18,16 @@ use Mailgun\Model\ApiResponse;
  */
 final class TotalResponse implements ApiResponse
 {
-    /**
-     * @var \DateTime
-     */
     private $start;
-
-    /**
-     * @var \DateTime
-     */
     private $end;
-
-    /**
-     * @var string
-     */
     private $resolution;
-
-    /**
-     * @var TotalResponseItem[]
-     */
     private $stats;
 
-    /**
-     * @param string              $resolution
-     * @param TotalResponseItem[] $stats
-     */
-    private function __construct(\DateTime $start, \DateTime $end, $resolution, array $stats)
+    private function __construct()
     {
-        $this->start = $start;
-        $this->end = $end;
-        $this->resolution = $resolution;
-        $this->stats = $stats;
     }
 
-    /**
-     * @return self
-     */
-    public static function create(array $data)
+    public static function create(array $data): self
     {
         $stats = [];
         if (isset($data['stats'])) {
@@ -62,33 +36,26 @@ final class TotalResponse implements ApiResponse
             }
         }
 
-        $start = isset($data['start']) ? new \DateTime($data['start']) : null;
-        $end = isset($data['end']) ? new \DateTime($data['end']) : null;
-        $resolution = isset($data['resolution']) ? $data['resolution'] : null;
+        $model = new self();
+        $model->start = isset($data['start']) ? new \DateTimeImmutable($data['start']) : null;
+        $model->end = isset($data['end']) ? new \DateTimeImmutable($data['end']) : null;
+        $model->resolution = $data['resolution'] ?? null;
+        $model->stats = $stats;
 
-        return new self($start, $end, $resolution, $stats);
+        return $model;
     }
 
-    /**
-     * @return \DateTime
-     */
-    public function getStart()
+    public function getStart(): ?\DateTimeImmutable
     {
         return $this->start;
     }
 
-    /**
-     * @return \DateTime
-     */
-    public function getEnd()
+    public function getEnd(): ?\DateTimeImmutable
     {
         return $this->end;
     }
 
-    /**
-     * @return string
-     */
-    public function getResolution()
+    public function getResolution(): ?string
     {
         return $this->resolution;
     }
@@ -96,7 +63,7 @@ final class TotalResponse implements ApiResponse
     /**
      * @return TotalResponseItem[]
      */
-    public function getStats()
+    public function getStats(): array
     {
         return $this->stats;
     }
diff --git a/src/Model/Stats/TotalResponseItem.php b/src/Model/Stats/TotalResponseItem.php
index f91ce0b..56e1cbd 100644
--- a/src/Model/Stats/TotalResponseItem.php
+++ b/src/Model/Stats/TotalResponseItem.php
@@ -16,90 +16,49 @@ namespace Mailgun\Model\Stats;
  */
 final class TotalResponseItem
 {
-    /**
-     * @var \DateTime
-     */
     private $time;
-
-    /**
-     * @var array
-     */
     private $accepted;
-
-    /**
-     * @var array
-     */
     private $delivered;
-
-    /**
-     * @var array
-     */
     private $failed;
-
-    /**
-     * @var array
-     */
     private $complained;
 
-    /**
-     * @return self
-     */
-    public static function create(array $data)
+    public static function create(array $data): self
     {
-        return new self(
-            isset($data['time']) ? new \DateTime($data['time']) : null,
-            isset($data['accepted']) ? $data['accepted'] : [],
-            isset($data['delivered']) ? $data['delivered'] : [],
-            isset($data['failed']) ? $data['failed'] : [],
-            isset($data['complained']) ? $data['complained'] : []
-        );
+        $model = new self();
+        $model->time = isset($data['time']) ? new \DateTimeImmutable($data['time']) : null;
+        $model->accepted = $data['accepted'] ?? [];
+        $model->delivered = $data['delivered'] ?? [];
+        $model->failed = $data['failed'] ?? [];
+        $model->complained = $data['complained'] ?? [];
+
+        return $model;
     }
 
-    private function __construct(\DateTime $time, array $accepted, array $delivered, array $failed, array $complained)
+    private function __construct()
     {
-        $this->time = $time;
-        $this->accepted = $accepted;
-        $this->delivered = $delivered;
-        $this->failed = $failed;
-        $this->complained = $complained;
     }
 
-    /**
-     * @return \DateTime
-     */
-    public function getTime()
+    public function getTime(): ?\DateTimeImmutable
     {
         return $this->time;
     }
 
-    /**
-     * @return array
-     */
-    public function getAccepted()
+    public function getAccepted(): array
     {
         return $this->accepted;
     }
 
-    /**
-     * @return array
-     */
-    public function getDelivered()
+    public function getDelivered(): array
     {
         return $this->delivered;
     }
 
-    /**
-     * @return array
-     */
-    public function getFailed()
+    public function getFailed(): array
     {
         return $this->failed;
     }
 
-    /**
-     * @return array
-     */
-    public function getComplained()
+    public function getComplained(): array
     {
         return $this->complained;
     }