diff --git a/src/openvic-simulation/utility/Concepts.hpp b/src/openvic-simulation/core/template/Concepts.hpp
similarity index 93%
rename from src/openvic-simulation/utility/Concepts.hpp
rename to src/openvic-simulation/core/template/Concepts.hpp
index d8dbe67c..3f1209a2 100644
--- a/src/openvic-simulation/utility/Concepts.hpp
+++ b/src/openvic-simulation/core/template/Concepts.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <concepts>
+#include <cstddef>
 #include <memory>
 #include <string_view>
 #include <type_traits>
@@ -81,8 +82,8 @@ namespace OpenVic {
 	// This adds to capacity rather than size so that it can be used multiple times in a row.
 	// If it added to size, it would only reserve enough for max(arguments...)
 	template<typename T>
-	concept reservable = requires(T& t, size_t size) {
-		{ t.capacity() } -> std::same_as<size_t>;
+	concept reservable = requires(T& t, std::size_t size) {
+		{ t.capacity() } -> std::same_as<std::size_t>;
 		t.reserve(size);
 	};
 
@@ -108,15 +109,14 @@ namespace OpenVic {
 	};
 
 	template<typename T>
-	concept has_index = requires { typename T::index_t; }
-	&& derived_from_specialization_of<typename T::index_t, type_safe::strong_typedef>
-	&& requires {
-		static_cast<std::size_t>(
-			static_cast<type_safe::underlying_type<decltype(std::declval<T>().index)>>(std::declval<T>().index)
-		);
-	};
+	concept has_index = requires { typename T::index_t; } &&
+		derived_from_specialization_of<typename T::index_t, type_safe::strong_typedef> && requires {
+			static_cast<std::size_t>(
+				static_cast<type_safe::underlying_type<decltype(std::declval<T>().index)>>(std::declval<T>().index)
+			);
+		};
 
-	//helper to avoid error 'index_t': is not a member of T
+	// helper to avoid error 'index_t': is not a member of T
 	template<typename T, typename = void>
 	struct get_index_t {
 		using type = std::size_t;
diff --git a/src/openvic-simulation/dataloader/Dataloader.cpp b/src/openvic-simulation/dataloader/Dataloader.cpp
index 9607260a..37036115 100644
--- a/src/openvic-simulation/dataloader/Dataloader.cpp
+++ b/src/openvic-simulation/dataloader/Dataloader.cpp
@@ -19,7 +19,7 @@
 #include "openvic-simulation/utility/Logger.hpp"
 #include "openvic-simulation/utility/StringUtils.hpp"
 #include "openvic-simulation/utility/Containers.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 using namespace OpenVic;
 using namespace OpenVic::NodeTools;
diff --git a/src/openvic-simulation/dataloader/Dataloader.hpp b/src/openvic-simulation/dataloader/Dataloader.hpp
index 54662d23..ef268f27 100644
--- a/src/openvic-simulation/dataloader/Dataloader.hpp
+++ b/src/openvic-simulation/dataloader/Dataloader.hpp
@@ -9,7 +9,7 @@
 #include "openvic-simulation/dataloader/NodeTools.hpp"
 #include "openvic-simulation/dataloader/ModManager.hpp"
 #include "openvic-simulation/utility/Containers.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 #include <function2/function2.hpp>
 
diff --git a/src/openvic-simulation/dataloader/NodeTools.hpp b/src/openvic-simulation/dataloader/NodeTools.hpp
index 5886e8fa..a4982467 100644
--- a/src/openvic-simulation/dataloader/NodeTools.hpp
+++ b/src/openvic-simulation/dataloader/NodeTools.hpp
@@ -26,7 +26,7 @@
 #include "openvic-simulation/utility/Getters.hpp"
 #include "openvic-simulation/utility/TslHelper.hpp"
 #include "openvic-simulation/utility/Containers.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 #include <function2/function2.hpp>
 
diff --git a/src/openvic-simulation/dataloader/Vic2PathSearch_Windows.hpp b/src/openvic-simulation/dataloader/Vic2PathSearch_Windows.hpp
index acd87366..c1c456c5 100644
--- a/src/openvic-simulation/dataloader/Vic2PathSearch_Windows.hpp
+++ b/src/openvic-simulation/dataloader/Vic2PathSearch_Windows.hpp
@@ -10,7 +10,7 @@
 #include <Windows.h>
 
 #include "openvic-simulation/utility/Containers.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 namespace OpenVic::Windows {
 	inline memory::wstring convert(std::string_view as) {
diff --git a/src/openvic-simulation/modifier/ModifierSum.cpp b/src/openvic-simulation/modifier/ModifierSum.cpp
index 03988fa6..1c4daba4 100644
--- a/src/openvic-simulation/modifier/ModifierSum.cpp
+++ b/src/openvic-simulation/modifier/ModifierSum.cpp
@@ -4,7 +4,7 @@
 
 #include "openvic-simulation/country/CountryInstance.hpp"
 #include "openvic-simulation/map/ProvinceInstance.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 using namespace OpenVic;
 
diff --git a/src/openvic-simulation/types/Colour.hpp b/src/openvic-simulation/types/Colour.hpp
index 87f1c2c8..c9386dc4 100644
--- a/src/openvic-simulation/types/Colour.hpp
+++ b/src/openvic-simulation/types/Colour.hpp
@@ -26,7 +26,7 @@
 #include <range/v3/algorithm/rotate.hpp>
 
 #include "openvic-simulation/types/StackString.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/StringUtils.hpp"
 #include "openvic-simulation/utility/Typedefs.hpp"
 
diff --git a/src/openvic-simulation/types/CowPtr.hpp b/src/openvic-simulation/types/CowPtr.hpp
index 77bd2f82..ef9b4897 100644
--- a/src/openvic-simulation/types/CowPtr.hpp
+++ b/src/openvic-simulation/types/CowPtr.hpp
@@ -7,7 +7,7 @@
 #include <type_traits>
 #include <utility>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Typedefs.hpp"
 
 namespace OpenVic {
diff --git a/src/openvic-simulation/types/CowVector.hpp b/src/openvic-simulation/types/CowVector.hpp
index edd7fd6f..1455c7df 100644
--- a/src/openvic-simulation/types/CowVector.hpp
+++ b/src/openvic-simulation/types/CowVector.hpp
@@ -14,7 +14,7 @@
 #include "openvic-simulation/types/BasicIterator.hpp"
 #include "openvic-simulation/utility/Allocator.hpp"
 #include "openvic-simulation/utility/Compare.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Typedefs.hpp"
 
 namespace OpenVic {
diff --git a/src/openvic-simulation/types/FixedVector.hpp b/src/openvic-simulation/types/FixedVector.hpp
index 6b221e26..38324b2e 100644
--- a/src/openvic-simulation/types/FixedVector.hpp
+++ b/src/openvic-simulation/types/FixedVector.hpp
@@ -5,7 +5,7 @@
 #include <memory>
 #include <utility>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Typedefs.hpp"
 
 namespace OpenVic::_detail {
diff --git a/src/openvic-simulation/types/HasIdentifier.hpp b/src/openvic-simulation/types/HasIdentifier.hpp
index c2738b55..4270880e 100644
--- a/src/openvic-simulation/types/HasIdentifier.hpp
+++ b/src/openvic-simulation/types/HasIdentifier.hpp
@@ -8,7 +8,7 @@
 #include <fmt/base.h>
 
 #include "openvic-simulation/types/Colour.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Getters.hpp"
 
 namespace OpenVic {
diff --git a/src/openvic-simulation/types/HasIndex.hpp b/src/openvic-simulation/types/HasIndex.hpp
index ec3d741f..1fcbc731 100644
--- a/src/openvic-simulation/types/HasIndex.hpp
+++ b/src/openvic-simulation/types/HasIndex.hpp
@@ -2,7 +2,7 @@
 
 #include <type_safe/strong_typedef.hpp>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 namespace OpenVic {
 	template<typename TypeTag, derived_from_specialization_of<type_safe::strong_typedef> IndexT>
diff --git a/src/openvic-simulation/types/IdentifierRegistry.hpp b/src/openvic-simulation/types/IdentifierRegistry.hpp
index 99d2c73e..577bd61e 100644
--- a/src/openvic-simulation/types/IdentifierRegistry.hpp
+++ b/src/openvic-simulation/types/IdentifierRegistry.hpp
@@ -5,7 +5,7 @@
 
 #include "openvic-simulation/dataloader/NodeTools.hpp"
 #include "openvic-simulation/types/fixed_point/FixedPointMap.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Getters.hpp"
 #include "openvic-simulation/utility/Logger.hpp"
 
diff --git a/src/openvic-simulation/types/IndexedFlatMap.hpp b/src/openvic-simulation/types/IndexedFlatMap.hpp
index 104075a0..04ca32af 100644
--- a/src/openvic-simulation/types/IndexedFlatMap.hpp
+++ b/src/openvic-simulation/types/IndexedFlatMap.hpp
@@ -11,7 +11,7 @@
 #include <function2/function2.hpp>
 
 #include "openvic-simulation/types/FixedVector.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Getters.hpp"
 #include "openvic-simulation/utility/ForwardableSpan.hpp"
 #include "openvic-simulation/utility/Logger.hpp"
diff --git a/src/openvic-simulation/types/OrderedContainers.hpp b/src/openvic-simulation/types/OrderedContainers.hpp
index 2384887c..2aef44e0 100644
--- a/src/openvic-simulation/types/OrderedContainers.hpp
+++ b/src/openvic-simulation/types/OrderedContainers.hpp
@@ -6,7 +6,7 @@
 #include <tsl/ordered_map.h>
 #include <tsl/ordered_set.h>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/Containers.hpp"
 #include "openvic-simulation/utility/Deque.hpp"
 #include "openvic-simulation/utility/StringUtils.hpp"
diff --git a/src/openvic-simulation/types/OrderedContainersMath.hpp b/src/openvic-simulation/types/OrderedContainersMath.hpp
index adf8e568..5527ba03 100644
--- a/src/openvic-simulation/types/OrderedContainersMath.hpp
+++ b/src/openvic-simulation/types/OrderedContainersMath.hpp
@@ -4,7 +4,7 @@
 #include <type_traits>
 
 #include "openvic-simulation/types/OrderedContainers.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 namespace OpenVic {
 	template <typename KeyType, unary_negatable ValueType>
diff --git a/src/openvic-simulation/types/TypedSpan.hpp b/src/openvic-simulation/types/TypedSpan.hpp
index f59730e8..68953ff5 100644
--- a/src/openvic-simulation/types/TypedSpan.hpp
+++ b/src/openvic-simulation/types/TypedSpan.hpp
@@ -4,7 +4,7 @@
 
 #include <type_safe/strong_typedef.hpp>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/ForwardableSpan.hpp"
 
 namespace OpenVic {
diff --git a/src/openvic-simulation/types/Vector.hpp b/src/openvic-simulation/types/Vector.hpp
index b60adc06..00b833ad 100644
--- a/src/openvic-simulation/types/Vector.hpp
+++ b/src/openvic-simulation/types/Vector.hpp
@@ -7,7 +7,7 @@
 
 #include "openvic-simulation/types/BasicIterator.hpp" // IWYU pragma: keep
 #include "openvic-simulation/types/fixed_point/FixedPoint.hpp"
-#include "openvic-simulation/utility/Concepts.hpp" // IWYU pragma: keep
+#include "openvic-simulation/core/template/Concepts.hpp" // IWYU pragma: keep
 #include "openvic-simulation/utility/Math.hpp" // IWYU pragma: keep
 #include "openvic-simulation/utility/Typedefs.hpp" // IWYU pragma: keep
 
diff --git a/src/openvic-simulation/utility/Allocator.hpp b/src/openvic-simulation/utility/Allocator.hpp
index 5408ca02..47474353 100644
--- a/src/openvic-simulation/utility/Allocator.hpp
+++ b/src/openvic-simulation/utility/Allocator.hpp
@@ -2,7 +2,7 @@
 
 #include <memory>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 namespace OpenVic {
 	template<typename InputIt, typename Sentinel, typename ForwardIt, typename Allocator>
diff --git a/src/openvic-simulation/utility/Compare.hpp b/src/openvic-simulation/utility/Compare.hpp
index 57da83fe..ffb3835e 100644
--- a/src/openvic-simulation/utility/Compare.hpp
+++ b/src/openvic-simulation/utility/Compare.hpp
@@ -3,7 +3,7 @@
 #include <compare>
 #include <type_traits>
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 namespace OpenVic {
 	[[nodiscard]] inline constexpr auto three_way_compare(auto&& left, auto&& right)
diff --git a/src/openvic-simulation/utility/Deque.hpp b/src/openvic-simulation/utility/Deque.hpp
index 92c499c0..95f80dcd 100644
--- a/src/openvic-simulation/utility/Deque.hpp
+++ b/src/openvic-simulation/utility/Deque.hpp
@@ -1909,7 +1909,7 @@ namespace OpenVic::utility {
 }
 #endif
 
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 
 namespace OpenVic {
 	template<typename T>
diff --git a/src/openvic-simulation/utility/reactive/MutableState.hpp b/src/openvic-simulation/utility/reactive/MutableState.hpp
index b1548e71..302dea2a 100644
--- a/src/openvic-simulation/utility/reactive/MutableState.hpp
+++ b/src/openvic-simulation/utility/reactive/MutableState.hpp
@@ -1,7 +1,7 @@
 #pragma once
 
 #include "openvic-simulation/types/Signal.hpp"
-#include "openvic-simulation/utility/Concepts.hpp"
+#include "openvic-simulation/core/template/Concepts.hpp"
 #include "openvic-simulation/utility/reactive/DependencyTracker.hpp"
 
 namespace OpenVic {